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.