seems like some creative soul could come up with a wad custom designed thusly: a non discarding plastic wad that would snap into the cavity of a lee key drive slug (sort of 2 half-moon convex base in wadcup)that would provide support for the slug, petals of a proper thickness and height, and of course a good OP base appropriate for a straight wall hull. mmmm.....the petals would have to shear off to allow the slug to fly downrange....looks like a challenge some engineering type would love!