Eric,
I had found your thread while getting the idea to build a bow, and used a piece of red oak as the tool. That's why the top limb came out nice. I think I just hit a weak spot in the board and when I removed where the pencil was on the bottom limb, the hinge started. I stayed away from it the rest of the tillering. But, yeah great post on that tool, mine's not as elaborate as yours though. Just used a cut off scrap from the board, made sure it was square, and put a hole in it. Thanks for the knowledge.