I use Boo strings w/ served on cat whiskers. They cost me 3-5 fps. You can put the stick on limbsavers in a variety of positions, each of which changes the fps cost.

Mr.T claims 15-20 fps per set. I had a used Excal that came w/ them on, one promptly flew off, I '86'd' the other.

I 'quieted' an Emax down some w/ heavier arrows, still lost some fps, which I could well afford, but gained K.E. IMHO, the heavier Excals set up for max fps are nasty buggers, lol. YMMV.