Be sure your centerline runs with the longitudal grain. Whatever it does, so should your centerline.
Forgive me if I'm wrong, but your pictures look as though you have marked lines down the stave with a straight edge. For a super straight piece of wood you can do that, but on most osage the grain wanders back and forth the length of the stave.
Pat and Eric are right. Depending on how long you want the bow to be, and your draw length, you should never need more than 1-1/2" wide for osage. Saw Filer