Pete: I bore out those holes because it was rotten wood. When I took it down to one ring last July I filled em best I could with titebond on the back but it was still just at floor tiller thickness. When I began working the belly the knots just gave way and instead of risking a potential crack coming from the rotted wood I just cleaned them out the best I could. I've seen some crazy bows with holes in the past. As long as you can tiller slowly and correctly working the bow in with each removal of wood osage can be very resilient.
Red Hill: The pillar makes it much simpler to get to brace height. Getting a good curve at brace makes tillering much simpler.