I have made a few multi-lam bows and I used 1/8" center lam and started with 1/8" belly lam that were reduced while tillering. I would only use the osage for belly wood and a lighter wood for a center lam. These would be for boo backing or hickory backing. Quarter sawn or bias sawn are preferred but flat grain will work also.
I, personally, would made a self bow out of a knotty stave. They look cool when done and it will teach you more about bow building than you could imagine.
If you take your time with it and only work on it when you really want to you can make yourself proud with a beautiful character bow.
Pat