I don't see too much problems with it as long as the patches are large enough to grip the ball.
Remember, the first patch has to grip the ball's diameter, the second patch needs to grip the ball's diameter plus the added thickness of the first patch, otherwise you are not going to get a good seal and there will be gas blow-by.
If you are worried about them slipping during loading, try having someone sew two patches together with a few stitches in the center of the patch, (not the edge) just to tack them together. See if that works. :thumbsup: