*sigh*
If you must
In my experience thick ringed locust has the greatest variance tree to tree, some of it having made good bows and some failing to survive heat. If you have a lot of experience with raw black locust you end up being able to feel the lousy wood not just by weight and hardness, but by texture, minute details in the surface of the wood, color, the way it splits, the smell, all that stuff that tells you you've spent too much time with a tree. The sharper, more consistent, darker, clean-splitting, sharp smelling stuff always promises high performance bows with minimal hassle.
That said, take a goooood loooooooooooooooooong time heating black locust to a warm brown color. It's not the end of the world if it chars, but try to stop just before.