I don't have any information about Knoxx products but at $150 you might want to try something cheaper first. I have a short-barreled Mosin-Nagant rifle that kicked like a a drunk Mike Tyson. It was tamed into a kitten by a $9 slip-on recoil pad from Academy Sports.

Another thing would be to switch to lower-powered self defense rounds. I don't remember the name of any off the top of my head, but my CCW instuctor recommended them for home-defense shotguns used by small-statured people or those not used to shooting.

-Blast