I’m shooting 60# @ 29 1/2″ out of a Bear Grizzly, and currently, I shoot Easton Gamegetter 2117’s cut at 31 1/2″, with a standard aluminum insert and 145 gr. field tip (150 gr. Wensel Woodsman). My FOC calculated out to 13.49%. Over the weekend, I got ahold of some carbon shafting that fits snugly inside my aluminum shaft. I’m planning to put between 6 and 8″ of carbon shafting inside my aluminum behind the insert (possibly with a 15 gr. insert in the carbon shafting). How much is this likely to affect my arrow spine? Is it likely that I’ll have to cut my aluminum shaft shorter to compensate for the extra weight up front? Any advice or other suggestions would be appreciated. Thanks.