Bues, I can assure you that Badger has more knowledge on principles of mass and limb thickness versus width than many ever will. The core wood is just what he said it is, a spacer. Any solid wood will be fine. There are a few species that have bad growth rings and are almost guaranteed to separate no matter where you use them, but they are few and far between. There is a slight difference in core woods since they can add physical weight to the bow, but it is only by adding extra physical weight that they effect cast. It is in fact a spacer separating the two working surfaces of the bow. A bow twice as wide is twice as strong. A bow twice as thick is eight times as strong. By adding thickness you add strength and by doing it without adding mass you can get a little extra benefit. Mass at limbtip will have more effect, while mass at midlimb will have little. Since the spacer (core) is from the riser out and there will be little weight difference between two 1/16" thick pieces of wood of different species, the effect of mass is negledgable. Justin