An update on this build:
I got the backing off with a little heat. I remember PatB mentioning that heat will lift TB3 glue, and it worked well if anyone needs to do it.
I glued on another boo backing and started retillering. There is a weak spot on one of the limbs due to node spacing differences between the 2 backings, and I have to reduce too much weight to fix it. It will end up being less than 50 lbs so I'm putting it on the side for now.
I did gain a bunch of experience with this build, so much thanks to Rich and others who helped me.
I'm moving back to the osage stave originally posted. It's roughed out to the dimensions that Rich suggested.