Personally, I’d leave the board as a singlefin. I wouldn’t even screw around with a 2+1. The basic layout is aimed at using the rail line itself as your motor, not the fin(s). You’re going to milk the wave for it’s energy and go with the flow, not pump a fin cluster (or fins/keels at the rail) to get out in front of the wave.
If you want to do a twin then do a design that’s oriented about what a twin does.
From your pic it looks to me like you clustered the side fins too close to the leading edge of the main fin. More similar to what the hull guys were doing when they added little nubs in line with a flex fin. In that setup the sides are really small, like 2.1/2", not 4" like a standard longboad sidebite. Do you have a narrow base flex-fin for the main and 2 nubby side fins that small? 'Cause if you don’t then it’s no wonder you didn’t like the 2+1