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I got a 2nd hand Riviera Door 7'6" sup. Looks to me like a pretty good SUP foil platform. I am going to abandon my FrankenFoil DIY through hulls and do it right, with pro mast track inserts. 
Any advice on mounting location? This guide says 18-22" from tail.
foilmount.com/blogs/installation/foilmount-hydrofoil-placement-guide
Other internet sources say the magic number is 20", so that seems about right.
The centre fin box ends at 16" from tail, so I am thinking of starting the install at 18". The track is a 10" chinook, so that gives me some room to move with mast, roughly 18.5"-24" from tail. Make sense?
The foil position should not be measured from the rear, as it then depends too much on the shape of the board.
You should find where your feet should be to be able to paddle comfortably in surfing position, and put the foil so that the leading edge of the wing ends up in the middle of the feet. On a "Tomo" shape, this often means the front foot 4"-6" before the handle. The handle is a better indicator of the paddling position than the tail.
For instance, look at John's video here: you can see where his feet are, and at 0:34 you can see that the front of his wing is close to the middle of his stance.
Colas please stop this one eyed rant on forward mast mounts . Unlike you we have tried it (as JB said) and here's why it doesn't work as well as rear mounted mast mount.
1/ You get excessive tail strike killing the pump shortening your ride and pump back out.
2/ On bigger waves the forward mount gives too much lift on take off , spitting you over the front.
3/ When you come down off a touch down you have more board to push you back up without sticking the nose.
4/ When you come round off a cutback there is more board to push off the foam ball. ( Austin & Dave Kalama are kings at this )
5/ The less tail you have behind the foil when carve avoids contact slowing you down.
6/ The handle mount means Jack Sh!t on mast mount pending on what weight foil you have to carry the board at a good balance point , if you have a lighter carbon foil it will be further forward if you have a heavier Ali foil it will be further back. Black and white.
You're only positive point is you don't have to shift your feet , so what all surfers move their feet. You also say you fly faster sorry that's just not true. We just had all the French Takuma crew out here and their mast mounts were way back and this is where I got the idea of a single front strap they were all using it and ripping BTW. So this just leaves you in the Foil universe preaching forward mast mounts fully strapped. You also stated my Kalama board was set up wrong by Dave Kalama 
Big call champion on an open forum.
Yes this is an open forum and we are all here to share our foil experiences and back it up with videos , right or wrong we all share the vision to back up our comments. My offset foot thing is just how I ride but I don't preach it and I don't like straps but if you want to use them , power to you. JB is right my feet should be centered I'm trying. It's about sharing and not preaching, so please let go and talk about something else and stop hijacking our threads. Unless you have a video of Colas session number 78 ripping it up to prove us all wrong. Peace out 
OK, Thought this may be a good time to get tech
Below is a high detail drawing of the balance points and the combined lifting moment of the foil. Look carefully then read my comments below.
1. I do not think the foil position has really anything to do with the the handle on the board, but it is possibly part of the equation. For perfectly balanced flight you ideally want all the forces aligning. But to get this you would need control over every force and it will never happen. So we try and work out where we can get the best alignment.
2. There is essentially a balance point of the board on it's own and a balance point of your self standing relaxed and still. This combined with your preferred stance to allow you to paddle should result in an un-realistic center of balance (because we can not 100% control it). Ideally if we could draw a force diagram and work out the cord and maximum lifting direction of the foil, we would try to match these two opposing up and attempt to create perfect balance. If that is what we are looking for?????
3. Having a perfectly balanced board feels amazingly light and is great for downwinding and ultra small waves. However this does result is a more twitchy ride and more difficult to control powerful turns and fluid changes of direction. Moving the "foil center" behind the "unrealist Center" gives us swing weight. This swing weight is used to help guide and give a force for us to work against. This will help in controlling turns especially as we get faster and ride bigger swells.
4. Most importantly. Everyone's perfect setup can and may be a little different as everyone's stance may be different. A heavier person may paddle in further forward to get better use of the volume of the board, hence changing the equation and bringing the foil forward to achieve their desired affect. I ride my foil about 4-5" further forward then Robby.
5. When experimenting with your setup, don;t just go to the polar opposites. Every inch makes a huge difference. I will ride my foil on the Hover 120 (7'6" @ 120 ltrs) between 19" - 20.5" from the tail of the board. On my prone boards I use markers to show where I like my foil for different conditions as seen below. This is the difference between riding not even breaking swells on the XL, to riding just breaking swells on the XL to where I start with the Large. Every movement back bring more swing weight into the equation and delivers more control allowing me to ride faster and turn harder. (these are marks to the center arrow on my Thrust Plate).
6. I've tried further forward and don't like the loss of control, as well I've tried further back and don't the feeling of having to work to keep my foil height stable. Make notes, try lots of things, don't just muscle around a set configuration and defend it like gospel. Get rid of the straps and get control for your setup.
Ride safe,
JB
Nice points JB, and thanks for your input! would add:
1. "I do not think the foil position has really anything to do with the the handle" - once airborne, no. The handle is only a good way to predict the paddle position, because it also involves flotation. Think of it: nobody would try to advise the paddling position by just the distance from the tail.
And on the physics of it, do not forget that your body weights ten times more than the board, and is part of the equation too.
But your point of having some "unbalanced" position airborne (of the board only) makes sense, I guess because you can thus leverage against it only in one direction (rocking backwards), which is easier to control with our body (ergonomics is not just pure physics). A bit like it is easier to paddle low volume boards by being a bit too backwards on the board, so you just have to push more or less forward, rather than having to alternate pushing/pulling.
And (speculation here!) it may be why we may have different view on this topic depending on if you use straps or not. I guess with straps, it is easier to perform push/pull control movements, whereas strapless, having only to balance in one direction is easier. Makes sense.
, but a concept. Yes if we were actually going to measure the forces the "un-realistic Balance Point would actually be in somewhat a different location, not perfectly in the middle.
That's a pretty interesting stance Piros. Looks like he stands very forward and surfs learning back? You'll even see in one of the slo-mo's he front foot is actually lifting as he unweights. His back foot looks to be infront of the mast opposed to ontop or behind.
JB
Bruno had the front foot on the rail 7 years ago... I really think that he didn't manage to develop the SUP foil because he was too good, and was managing to foil despite having the front foot on the side, and a negative wing angle, making it too hard to learn for regular people.
You can even hear him in the video saying "paddling with the foil is a chore, but so what, I like to work hard in sports"... never having thought in 7 years to just change the wing angle...
Yeww! Mast tracks installed on new to me door. Now just need waves (flat season til fall).
Finally found bolts long enough to work in my tuttle box. That was a quest. Now if only I had time to get on the water.
Busy again, this time i have gone small.
Its my tooth pick 6'2"
Was pretty tough to stand on to start with but you get used to it.
Colas said
"
- I can apply more force in turns, especially in two axes (... rocking and rolling!), whereas the foot-on-the-stringer gives you a more linear and progressive control. "
If if you change "turns" to 'turn a round' and Stringer was the name of a distortion pedal.
then this would be in a guitar forum
Hey Alex,
The measures I use are from the tail of the board to the rear of the mast. There is no magic measurement, it is specific to board length and balance point. The GoFoil graph is a great starting place for foil placement if you implement the understanding that forward will provide a more aggressive lift and more neutral balance, and aft will provide more control and direction at the cost of front weight (which is excellent in bigger conditions).
Everything with foiling is personal once you work it all out, but to start with it's good to be in roughly "the right place" until you work it all out. For instance I ride with my foil super forward and my rear wing at full lift (+3mm), where as Robby Naish rides his foil nearly all the way back with the same rear wing setting, but the Chuck and Michi ride their foils about mid way with neutral on the rear wing. So while it's all a bit confusing, I strongly suggest setting your rear wing at neutral (unless you're on the Naish XL, which I suggest starting at +1-1.5mm). And depending on your board size and ability, work around the lengths above.
- If you find you go up before you're ready and difficult to control the lift, move your foil back.
- If you find you constantly need to push on your back foot to promote lift even on a good glide, then move your foil forward.
Once you've roughly worked out your mounting position, then using the rear wing adjustment will suggest how aggressively the foil responds to input. I'd only play with this once you've got things dialled.
Hope this helps, Don't rush the process and only make very small adjustments.
Ride safe,
JB
New Smik sled for Xmas...just sharing the stoke..so different to my previous foil board at 7'8..this baby is 6'6 x 28.5 x 106L and full on...have had 3 sessions on it in pretty average foil conditions tbh....haven't quite found the sweet spot yet but working dam hard on it..( can see why guys lose weight ) first impressions..way more control in the air..but alot harder to get into waves right now..I'm sure that will improve ...thanks to all the good advise..especially Rob and Matt..legends
An interesting pic of the two setups used by different Gong riders on the same day in weak small waves for surf foiling:
On top, the setup of Beryl: 65kg with the 70cm wing (M) and kite stab (smaller size). A Young athlete able to pump back to the lineup.
Below, Patrice (The Gong shaper): 100kg with the 100cm wing (XXL) and surf/SUP stab. Top foiling technical level, but not as young, and thus does not feel it worth pumping back to the lineup as it is puke-inducing exhausting. Note that he even now surf foil with longer (but light) prone boards: he told me they are worth it for the ease to paddle back to the peak and take off on weak waves, even if they do not pump well: for him it is more fun to gain speed on a foil by carving turns rather than pumping, and a longer board is then less of a problem. (re-watch the seminal foil vids of Kaehi...)
The Gong XXL seems to be a cheap alternative for the Gofoil Maliko 280..
When will it be available ?
