Kevin,
Beautiful work, you are tempting me.
My favorite for weighted defense devices is a pair of discount store knee-high nylon socks, one inside the other, and a considerable weight of lead shot or BBs. An interesting variation is to substitute a pound of dried beans. Shot or beans have a knock-on effect because they don't rebound on impact.
Art,
You WANT it to have it bounce, it doubles the impulse. The shot or beans give a good thump without the likelyhood of crushing (or leaving as big a bruise) but you have to decide which you want, more effectiveness or less evidence.
Respectfully,
Jerry