I build all my own bows to be FF safe . Thats just in case I sell one or build one for someone else and they put a FF string on it . I shoot dacron on all my bows and from my (not too scientific) experiments with a friends (not real expensive) chronograph 8^). FF only gains you 3-5 FPS on most bows (that includes some well known customs , not just my own bows )
3-5 fps is NOT going to make a difference in a real world hunting situation. I'll take a quiet shot over 3-5 additional fps every time.
Once you initially break a dacron string in and get it stretched the "creep " that people talk about is minimal . And golly gosh ,how hard is it to put a couple of twists in it to bring it back up to the correct brace height anyway ?