I am not sure that thickness has anything to do with it..... The back glued and belly glued into reflex creates a sheer line at the glue line, this sheer line is glued past the neutral plain in reverse (reflexed) so as the bow is pulled it does cause the back, and belly to have a more equalized strain, and the glue line running through the limb to take more stress. otherwise..... internal sheer forces put at the limb inner working glue line. Thats how I understand it anyway.