The old 15.5g and 18g slugs work very well at 20fpe+ for me already. The 12.5 at 12fpe would be icing on the cake. I should be able to get 24/25fpe so it will be interesting for sure. As for capturing them I'm not sure I can get a water bag pass though set up but there is a 1" stall matt at 60yd to stop them. The older style would expand fully against the matt, never penetrating. Meanwhile 10.3g AA heavies will zip through at the same energy(from the muzzle).