Of course I'm building board bows, not from a proper stave, but I'm using good pieces...I only really get irritated when I have a PERFECT grain and I get the same results. The bow I'm working on right now is still 1.75" at the widest, and comes down to .625" at the nocks. Backed with bamboo. It pulls 58lbs at 29" (my scale may be reading about 5lbs light, though). Tiller is smooth, stiff ends, so I know a lot of the force is put mid-limb.
My issue is that every red oak bow I've made...and I've made lots of different kinds...has developed set. I had one have so much that it seemed to pull the recurve out of the ends.
I've never tried belly tempering. Could this help? Is it just a part of working with red oak?