Fins; again.

I admit it, I have a fetish for trying different fin combinations, but I really enjoy the different feelings it creates in a board.
I would love some input on my latest venture.

On my 8'7" Sunova Flow, I am playing with switching from larger thrusters and a small center fin to smaller thrusters and a larger center fin (a 2+1 set up). I have been riding the board with a variety of thrusters in the 4.5" to 5" range, usually 4 ¾". For the trailing fin, I have been ranging from 4" to 4 ¾", most often 4 ½. I tried going to a very narrow 4" center fin to loosen the board up, but started getting some spin out. Recently a SUP coach told me that if I wanted looser, I should quit trying to go smaller with my center fin, and start trying smaller thrusters. So today I went down to 3.5" thrusters with a 5 ?" center fin, which worked fantastic in the very small waves we had today. Anyone have any thoughts on this set up?
My next issue is what to do with this set up in larger surf. If I want to stick with the small thrusters, I should probably go to a larger center fin, but my board has all FCS boxes, and I cannot find a center fin larger than 5 ?". Does anyone know of center fins larger than that with FCS tabs?

My understanding is that in a true thruster set up where the side fins are larger, they are the dominant turning fins like a twin fin, and the center fin tones them down and creates forward drive. In a 2+1, the larger center fin becomes the dominant turning fin, and the sidebites just create a little more bite on the wave face, allowing a smaller center fin. Historically I have always preferred single fins on my surfboards and wavesailing boards, so this move to a center fin dominant setup appeals to me. However, my observation is that 2+1 set ups usually have a center fin of at least 6 to 7 inches. Anyone have any thoughts about using a 5 ?" center in a 2+1?

Thanks for any help.

It also depends on your style: If you push seriously on your fins in turns, you want them big enough to give you leverage and acceleration. If not, they will just bog you down.

It may be in your case that your push in the turn is really aft, and you need fin surface on the rear, hence the 2+1.

It would advise you to try the C-Drive fins: they have a lot of hold, but close to the hull, so not too much torque to spare the FCS boxes, and not stiffen too much your rear foot (I do not like too much surface at the fin tip, because the "foil" effect at speed is hard to control)

On the opposite, Harley Ingleby fins have an interesting design: a combination of large surface (even at the tip) and depth for leverage, but with a thin profile for speed. They use a lot the "foil effect" to leverage on, but you must have the legs to handle them. Note that his thruster set have bigger sides than the trailer, so I guess he is the opposite of you.

You may also want to try 5 fins: you get a lot of grip to push on, but with a real smooth transition in rail-to-rail, and no foil effect as with bigger fins.

Thanks everyone for the good input.
Slugga: I have surfed the Flow as a quad, and really enjoyed it. The 2+1 idea is just my next way of exploring what the board will do with different fin setups.
Colas: Always admired your surfing. It is true that I am constantly working on getting my back foot as far back as possible, so that might play into why I am having fun playing with a 2+1 set up. I have also played with your idea of fins with a lot of chord at the base, and not much tip area. I hand re-shaped a few fins so that they kept the chord of a 5" fin, but got rid of most of the tip area and rake. I found that I can drive off them very hard, and get a little bit tighter turns with less down the line projection than a fin with more tip rake area.
Dean: Right on. Those cherry wood inserts that the FCS plugs are set into is one reason that I felt safe in trying a larger center fin. The largest FCS center fin I have found so far is Bert's 105 (about 5 ?") which is what I have been using successfully in small surf, so I am still looking for something around 6" for larger surf; it looks like no one makes anything in that size range with FCS tabs.

Obijohn, we are needing to work on this Fin Fetish Awareness....ITS HEALTHY.
My small board , 8'6 Space Pickle, gets setup for the waves of the day and/or my mood. Twin,Tri,Quad in Large to DIY small
and single's, from Wayne Lynch's Evolution on big days to a 70's Cutaway Dee fin for those clean little summer noserides.
Stay Healthy

I did watch that interview on paddlewoo, and found it interesting and sometimes confusing. The part about trying larger thrusters to loosen a board up is something that I am still trying to process. I should watch that interview again.

Shapers S9 5.25". Works a treat as you lads would say!