In the case of these bows, that is what I supposed was going on, but I've owned several custom bows, the shelves of which are much like that shown. I am going to get around to putting a new sting on this girl, adding some beaver ball string silencers and shoot it with a thin strike plate just to see what happens. It will probably rattle like a coke can full of pennies and if so I'll cut a more robust rest for it.
Thanks for your comment.