First, my thought with respect to design is to keep it simple: 60 inches tip-to-tip, and one inch wide from mid-limb through the handle to the midpoint of the other limb, then tapering down to half inch nocks. Will this work well for a hickory-backed-osage bow, assuming I do not botch the tillering? I will probably glue in about 2 inches of reflex, with the hope of ending up with a nearly flat side-view profile once the bow is shot in.
Also, how perfect does the belly core have to be as far as straight grain and knots? I have made a couple bamboo- and hickory-backed ipe bows, and was very picky about the belly cores, at great expense. Perhaps more picky than I needed to be.