There doesn't seem to be much preload on the springs, plus I guess the springs should be shorter, for him to be able to get to full draw. But playing around is allways fun. When I was a child / young, I also played around making bows of electric-pipes, I even made a "
compound bow" based on these pipes, made a more powerful than original bow, from a glassfiber bow from a sports shop, by making a handle section for it, to shorten the flexible part of the limbs etc.