I'll post this in the FWIW dept. ..
Robert Churchill(sp?)in his book titled 'Shooting' said that when shooting hares from a butt, that he found it most effective to shoot the ground roughly six inches to a foot underneath the critter, so that the gravel and dirt were ricocheted in toit along w/the now deformed shot, effectively multiplying what it was hit with, oft by a very substantive amount.
I have found that the same technique applied to sporty clays 'rabbits' can be wonderfully effective, particularly when confronted w/an edge on presentation of the half inch thick type targets. This, of course, only applies to those targets on the ground. When they jump, you have no choice aside from shooting them in the air & I am a believer in using #7.5 shot on sporty clays 'rabbits' because they don't always follow the terrain & I want as much pellet energy as is allowed. Regardless, one must hit it first, before getting into a shot size discussion, eh?
Nice shooting, Stan! And a neat trophy for the accomplishment, too.