Thanks for the advice guys.  I don't know why I said this was a stave, but it is a quad-lam bow so I can't heat it later.  I decided to tape one end of the string to one tip across the back, and used the other end on the other tip and just let it go slack slowly.  I was easily able to tell where the string was touching the center.  Thanks for your help guys!  I really hope this bow makes it through.  The laminations on this one will look just gorgeous if it doesn't break!