Get a PAST Ambidexterous Recoil Sheild. They are about 3/8 inch thick and rather flexible. Much better than any thin slip-on pad or any of pads sewn into clothes. We use Past Ambidexterous Recoil Sheilds consistantly because we both have bum shoulders, thanks to injuries and operations.

Depending on situation, we sometimes place them under our shirts, sometimes over.

Niklas