Hoyt08, here are the numbers for you. With your GT 500's using 3" Duravanes and the 85 gr heads your FOC will be 12.4. If you use the 4" Duravanes your FOC will be 11.3. If you go with the 100gr you will be around 14.1. I currently use GTUltralight 400's at 60# and 27" witha 85 gr head and get exceptional performance out to my max range of 45 yards. I have not used the BuzzCut but did use the 4 blade stingers last year without a hitch. I am sure you will do fine with either.