As I underrstand it.....Art.Sinew has no shrinkage, being nylon, it may stretch, but will not impart any real additional strength to the back of a bow. Real sinew shrinks as it cures, that's why the reflex increases as it dries. It's shrinking, pulling the limbs into additional reflex, increasing the poundage.
A.S. won't do that. Correct me if I'm wrong....