This may seem like a weird question, but I have been playing at bowjackson's site and found out how bad the foc is on mine and my husband's arrows. I'm going to switch to GT 3555 with 125 gr. tip and I think that is okay, but he shoots aluminum and there are a lot of variables! With the 2117 he has a stiffer spine, but the foc is only 9.4%. If he uses the 2213 the spine is listed as "C" on the charts, but his foc will be 11.1%. He shoots a 30" arrow at 55 lbs. currently a 2413 superlite with 100 gr. tips. What are your opinions?