I've added belly slats to several bows and also put a thin patch in over a hinged area with success. The hardest part of doing this is to get the belly flat and mate the slat to it very carefully. I use a hacksaw blade to roughen both of the mating surfaces, then glue with smooth on epoxy. I clamp sung, but don't starve the joint of glue. When cured 24hrs, unclamp, clean up and re tiller. All this being said, it is probably quicker and cheaper to just start over.