OK I plugged everything in to the Stu Miller's calculator and it states I need a 51.7# spined arrow. However, I use GT 33/55s cut to 30 inches with a 100gr brass insert and 175gr heads... the things fly like darts out of my bow and hit exactly where I look. They spine 34.4 on the calculator. Whern I use heavier spined arrows, or cut the 33/55s down they fly right and appear to be over spined? Just curious if anyone else has found a much weaker spined carbon to fly better out of a non center cut longbow (JD Berry Vixen - 51#s at 27.5 and I pull around 28.5 inch draw)