What would be an appropriate distance to have the thruster fin from the tail on a 6’4" performance board (4-6 foot reef breaks) for a front foot surfer, and how spread should the fin cluster be?
I’d urge you to search the archives here, this question has been answered many times.
The classic standard thruster setup is 3.5 inches on the tail fin (rear of fin to rear of board). The rail fins are at 10.5 inches and toed-in 1/4", and are 1 1/4" off the rail (at the rear of the fin). Cant 5-7 degrees.
More inboard is less drive, more outboard is more “pivot-y”. For tails narrower than 14", rail fins go further forward. More cant is less drive and more lift.
But there is a wide variety of answers, rear fins go from 3.5" to 5 inches up, and rail fins from 10.5 to 13 inches up, toe-in on rail fins can vary by a tiny bit (more toe on flatter tails boards)…,