I think it's more the over length 2" playing length that throws everything off plus FST 115 and Pro 115 are 43" blank raw and the FST 90 is 41"
With my swing I tend to like the smoother shafts ie. Recoil 660 SC F2, Wishon S2S Green R/S, FST Pro 115 A/R, Apollo Shadow Lite etal. But also my playing length is closer to std. or slightly over but not 2" like yours IMO this makes a huge difference. IMO you need a stiffer tip shaft or you will not load the shaft properly.....probably why the FST 90 and Recoil 760 didn't work out. FST 115 A/R are tip stiffer than the others. It's why I dislike it and you like it.
BTW....cuz you like wide soled irons/shovels and like high lofted drivers. I am guessing here but think you have a steep angle of attack? Are you a divot taker....deeper divots when turf allows and steep with irons?
BTW I paid $15.45/shaft for the Recoil 660SC so I find them a bargain.