I would think it would have to be closed loop. Material density is not always uniform (especially with something like wood) and that has one of the biggest effe

I would think it would have to be closed loop. Material density is not always uniform (especially with something like wood) and that has one of the biggest effects on how your tool behaves. Even then, compensating for sudden release in tension, where the tool tries to spring back, seems perhaps insurmountable.