I would look at RST shells that are made for 2 1/2" guns. They should be lower pressure and be more comfortable to shoot. Sub 6 pound guns are not that much fun to shoot with any loads.
You might be better off using another gun. If you want to keep with the 28 a Remington 1100 would be my first choice. More important to make the shooter comfortable than anything else at this point. I was about to go down this route with my youngest when he picked up one of our Ruger 28 and shot it like it was custom made for him. Saved me buying one more gun for now.
