One thing I have learned is to make your bow out of the best piece of wood you can get. Very straight grain with zero run out swirls. Elm makes a great core lam, walnut is ok. Even a suspect piece of Osage will work for a core lam. Osage belly, Osage core lam, backed with boo makes a sweet bow. Make the belly lam 1/4" parallel, the core lam 1/4" tapered to 1/8th at tips. Hickory backing 1/8th parallel. The hickory backing needs to be very straight grained.