Don't try to cut the glue line. I have tried it many times and all you do is ruin everything. Choose which you want to save, boo or hickory, and grind the other off. If you have more material to use you can always finish the bow for practice then start a new one. The other option is finishing it at a light weight, then gluing a thin lamination of something a little better in compression like Ipe or Osage to the belly of the limbs and make it a trilam.