Here's an alternative. Can you check out some steel-shot wads. I found the inner bottom is cupped on the ones I found. It cup is undersize to the size of the ball, but holds the ball perfectly centred. The wad is full size to all the hulls I tested it in. I've posted this picture elsewhere in another ball-load thread on this forum - somewhere. I guess it won't hurt to post it here as well. Too- the bottom of the gas check, although having a square sort of cuttout, perfectly seals on the powder end of things.