Like Mike O., I think nothing works better than JB weld for inserts on carbon. Big difference between it's strength and all the others I've used. Rough up the inside of the shaft (I use a .17 caliber stainless bore brush on a dremel tool), and the outside of the insert (whether brass or aluminum, I rough them with a larger stainless wire wheel on the dremel), prep both with acetone, + jb weld = no more mushroomed shafts even from my heavy bows. I may break the shaft behind the insert but not mushroom the shaft.