hopefully this post can save somebody money/time. i recently finished (i thought) tuning my bow/ arrow combination - martin bamboo viper, CE Heritage 350's. got to the point where accuracy was good, arrow flight was OK, only complaint was the bow was noisy - string was twanging. saw the dvd "masters of the barebow", where i learned nock fit can effect noise and arrow flight. filed down my nocks, so string fit was perfect. no more noise, but now arrows are over-spined, because i cut them too short. so my advice to other newbies like me, is if your tuning results show nock left, check your nock fit before you start cutting arrows. there should be just enough friction to hold the arrow on the string.