I’ve made my share of ERC self bows, and they are definitely high-risk. That said, I’ve found that the sapwood helps in tension, while the heartwood is better under compression to limit set, a bit like yew. It is possible, but difficult, to follow a ring, but if you can manage it and keep roughly 50/50 sapwood to heartwood thickness, you’ll have a good chance of an optimal ERC self bow. And it’ll look gorgeous!