well thanks, nowadays twin fins are being ridden a lot, i tryed some and i am not to big or too heavy surfer , but i was amazed with one in particular a 6’5 x 2,5 x 21 round pin retro C (from blendimg curves)
this board was heavy triple 6 oz and 2 hotcoats.
The funny fact is that being heavy made it the fastest board i have ever ridden.
its funny cause people always looking for lighter boards.
Good luck with the coanda project i know you are prone to prone but i think you shouldn’t abandon the possibility of one day work on the design to make a stand up board.
You’re set on 1 3/16 off the rail haha it’s a great number but don’t be scared. Go 1 3/8 if 1 1/2 is too much of a hurdle to get over. What is the height of the fin your using?