I use a toothing plane to level out the back of the Osage and add grooves for a better glue joint. I also do the same to the belly side of the boo before glue up. Your boo should be tapered also from 1/8th thick at the handle to 1/16th at the tips. I also have my boo cut out to the exact shape of the bow before glue up. I also taper the belly of the Osage like Pat says, having the tips 1/8th thinner than the fade area.