most of the photos here are of 1 bolt, with mast extension pin all together as one piece, with these the only compatibility issue is some of the Euro pins don't fit others. Obvious if the mast extension fitting system is the 2 pin on the side which is USCup, they all fit.
going to the base as shown 2bolt Chinook, most uppers will fit, it doesn't matter if US or a Euro pin above, WHAT doesn't fit and vise versa is Streamlined , they are not compatable. This apples the the mast base and upper, NOT mast extensions, which do fit each other.
FWIW the Streamlined has a shorter bolt spread, giveing more adjustment, could be critical if the mast track is short, as Witchcraft.
the 2 bolt ones are secure in the track, where I've seen the one bolt come adrift. This is aright PITA requiring 2 men a boy to put together on the water. Usually happens but once.
depending on useage , inspect and if in doubt replace the tendon, rubber mast base cup, Some of the replacements are not of such great quality.
That's the setup I have, works like a charm, and lasts a very long time. Eventually the allan wrench piece in the middle will turn and won't work for tightening the 2 bolt mast base, but the universal joint will still work for windsurfing. I just carry an Allen wrench of the same size in my truck to check the base once in a while.
I have had the universal joint for 10 years before it showed signs of the rubber cracking. There is plenty time to see the rubber cracking before it breaks. It tends to crack from the outside in, so the cracks are always visible.
The 2 bolt mast base is still solid, and I have used it for 10 years now.
Select to expand quoteMastbender said..
blazing928 said..
Imax1 said..
^^^^
Ive heard a harsher ride ?
I've heard that too. I have one, so I'm going to try this weekend. Can't imagine I will notice much difference on a raceboard....
They are fine for flat water sailing, but terrible for the ocean.
As for the tendons, they can fail w/o a warning also, I've had them split where the pin goes thru inside the top or bottom collar, it's hidden. If the uni isn't standing up straight after you disconnect the sail, it is splitting at one of the pins, time to replace. But I have no preference over which to use, I use them both, however I'm a dedicated fan of a two bolt base going into the mast box. A single bolt can break the box in big surf, seen it too many times.
Purchased this base, solid but can't get it all the way back in the track without one bolt sitting in the track opening
you lose about 3 cm or 1.5 inches ??
personally like the 2 bolt mast base AND the mechanical joint
have stayed with 2 clip US connection - works for me - joewindsurfer.blogspot.ca/2013/11/windsurf-mast-bases-and-extensions.html
some mast extensions wear @ the holes 
too bad we cannot control size of these pics #$%^&*()
I've used many different bases and uni's over the last 25 years.
The two bolt system saves time in rigging as you can leave the base in the board. An extra 20 seconds is big!
Downside for me of the two pin system is the extra few grams of weight 
The RRD base and uni that I bought a year back is working well.
The uni tendon and case is very stiff and the base is light.
I only ever position my base in the centre of the track - the optimum position.
Select to expand quotejoe windsurf said..
you lose about 3 cm or 1.5 inches ??
Thats a lot if u need it right to one end
My opinion only, most newer boards have dialed in exactly where the mast track should be, so the optimum place for the uni should be close to the center of the box, older boards, not so much. I have a single bolt uni that I have to use whenever I take out this particular older board that I like to ride just for the hell of it, which isn't to often. The box is too far back so I have to have the uni all the way forward, and that extra 3 1/2 cm can make a big difference in a situation like that.
Select to expand quoteMark _australia said..joe windsurf said..
you lose about 3 cm or 1.5 inches ??
Thats a lot if u need it right to one end
The measure is 31.5 mm, so yes you can get only as close as that to the end. The Streamlined 2 bolt is smaller, lighter, and gives about a cm more adjustment. Too lazy to un stack the board it's on.
i agree with MASTBENDER, that most are now centered, some adjustment however is desirable.
only board that wanted to the end (forward this case Tabou 3S, 2007) I used a single bolt.
I use these too - the double bolt base with and the boge uni with the base tool.
Besides it obviously not being able to use the full track - as stated by another poster.
I have found that the boge is not replacable and you will need to change the whole unit as shown below and that can be a bit pricey if you do it yearly.
Still prefer them them though and have sailed a few home just on the webbing when the boge has failed.Select to expand quote
That universal joint will last a long time. I just replaced mine after using it for 10 years, as it just started to show signs of cracking on the outside.
Good ol Windance Board Shop! They rock and so does Big Winds! Those are my go to shops!
Umm, Why would replacement parts be available foe something then..? Is it possible you have something else?
the yellow part on this, is where the large black rubber bit goes instead.. of the tendon.
It's true, the rubber is replaceable. It takes a little time to get in their and get the job done. It's a very tedious job though. Windance Board Shop walked me through it. Windance's staff does replacement for that particular rubber piece.
For me, just less headaches to just buy a new universal joint. Then you don't have to worry about any other pieces in the unit going bad. Peace of mind!!
^ that's why I say the Chinook one-piece europin with tendon.
The bolts are fatter, don't bend and come undone without rounding them. So many times I have needed a vice, 15 tools, soaking in WD40 overnight and an hour of cursing to change a tendon. Usually having to destroy the bolts in the process. Not with the new Chinook ones, tendon change in five min every time. Even at the beach if one needed to I reckon.
Select to expand quoteblazing928 said..Imax1 said..
^^^^
Ive heard a harsher ride ?
I've heard that too. I have one, so I'm going to try this weekend. Can't imagine I will notice much difference on a raceboard....
Finally sailed with the mech joint. As expected I couldn't tell any difference in ride. Easy to fit uni to extension as you can just turn the joint with out having to put board on its side.
Nigel
Select to expand quoteMrCranky said..Magic Ride said...
Love the Chinook 2 bolt mast base. The best setup I have used yet. Very strong and durable peice of equipment.
But how easy is to to change the position in the mast track?
Good point MrCranky. I use a two bolt system on the base. Doing adjustments is a pain and it takes slightly longer to set up. You can leave just the base in the board though - just remember to bring that board to your next session If you don't have a spare base. The big advantage with the two bolt base is strength and some added safety. I replace the pin section every 1-2 years as a fail safe measure, but I would not be surprised if they lasted a number of years before the rubber tendon gave way.
Beware of using the tool on the botton of the uni to tighten the bolts in the mast track, it requires a lot of grip strength to get the bolts tight. I saw one unscrew resulting in the base bouncing around on the deck causing holes to be punched through The area surrounding the mast track. Use an Allen key to tighten.
Also one sailor using a conventional single bolt "Spinner" had his board and rig separate in surf even though it had been tightened, leaving him in a very sketchy situation and a complete rig lost.
The Chinook system is arguably one of the safest.
I used to be a huge Mistral fan until I bought a dude 
I was a huge fan then because the Mistral Stinger came with a mechanical uni-joint. That unit lasted as long as my board until it finally delaminated. I would dearly like to have a good mechanical one again. But with the array of uni-joints I have gathered from various quick sales, I doubt I need to spend money for such necessary evil for a while.
I remember tightening a boogie join by hand ( it's all we ever had ) and it never moved , ever , no base plate , no nothing , just hand tight .
The cheaper 'copy' two bolt chinook type bases actually have a slightly curved base plate. (I assume the chinook ones do as well from the look of the picture in the thread earlier.) This means one does not have to strain to get the bolts really over tight, Moderately hand tight with the base tool is plenty. None have ever moved on me, but then I don't give them (much of) a thrashing in the surf either.
The old thin curved track plates were a very good idea. They created a spring washer effect and the edge of them could bite into the box track which made them more secure. Not sure if they can still be bought though.
I have only ever had one Euro pin break. It was brand new and on the first sail. It was brought as an assembled unit with a Bodge rubber joint. When I inspected it later I noticed it was pre fractured. I surmised that the assembler had been too zealous by over tightening it and had fractured it . From that time on, I have always bought the Bodge joints and euro pins separately, and assembled them (with a little Loctite) myself.
Select to expand quotesailquik said..
The cheaper 'copy' two bolt chinook type bases actually have a slightly curved base plate. (I assume the chinook ones do as well from the look of the picture in the thread earlier.) This means one does not have to strain to get the bolts really over tight, Moderately hand tight with the base tool is plenty. None have ever moved on me, but then I don't give them (much of) a thrashing in the surf either.
The old thin curved track plates were a very good idea. They created a spring washer effect and the edge of them could bite into the box track which made them more secure. Not sure if they can still be bought though.
I have only ever had one Euro pin break. It was brand new and on the first sail. It was brought as an assembled unit with a Bodge rubber joint. When I inspected it later I noticed it was pre fractured. I surmised that the assembler had been too zealous by over tightening it and had fractured it . From that time on, I have always bought the Bodge joints and euro pins separately, and assembled them (with a little Loctite) myself.
Please help DavMen out as he can't replace the boge/ rubber bit.
the 2 bolt system has 2 major plus. The base stays on the board, insert , slide clip, you can remove the same or use the mast ext, pins or button to remove from mast Extension.
the other over One bolt, is should it become loose, it won't, come out of the track, the bots hold it in, while it will slide.
the degree of tightnessof the bolts , is not overtighten , snug.
Is this addressed to me? ^
Happy to help but DavMen is in the next state and could be a thousand km away so it won't be hands-on today.
OK. Here goes with web help.:
The base bolt is screwed into the Bodge joint female thread, probably with Loctite. I have found that old ones are sometimes very reluctant to part company.
Put the rubber joint in a vice (or Stilson pipe wrench) and get a socket spanner (6mm?) onto the bolt to remove.
If successful: buy new PJ with female thread and but the bolt in the new one with some Loctite. Do not overtighten with large lever to it may fracture and will break on your first sail (or soon thereafter)!
If unsuccessful, grind or cut away all the rubber to remove the metal part containing the thread from the PJ. It actually has a hex bolt head on it which you can attach a spanner to to hold it better and use socket spanner to get it undone. (I actually did this last week)
If that is unsuccessful, (you break something?), go to the shop and buy a new base insert part to screw into that new PJ you bought in anticipation of it coming undone. 
From what I'm understanding in your description the inner part of the Chinook tool is a hexagonal head set screw
and with much convincing sould be able to be undone
Will give it a go next time.
I think might give the Chinook base a go but I want to keep my NP MXT RDM extensions, these are just great with high quality pulleys. Can I just use the UXT adaptor so it will take the Chinook / Euro pin is it that simple ?
Select to expand quoteDavMen said..
From what I'm understanding in your description the inner part of the Chinook tool is a hexagonal head set screw
and with much convincing sould be able to be undone
Will give it a go next time.
Yes.
