From what I understand FF can only be shot on limbs with reinforced tips. something about the non stretch of FF that will break the tips off. Bear limbs with the four layer tips (white, black,white, then black again)are rated for Fast Flight use . I have 2 sets . I use them on an early 90's riser to make a 60" bow (one set at a time of course ) I personally would not use fast flight on a bow not specifically designed for it you just are not going to gain that much . an extra 8 to 10 ft a second aint worth destroying a good bow .
Just my opinion !
huntnfool