I'd buy a MEC 600 and load a low pressure shell. I shoot a 7/8 ounce 1100 fps load, no worries. If you don't want to reload, I'd go with 20 gauge adapters.

You can buy RSTs for what 28s cost. I just can't get excited about 28 gauge when the guns weigh the same and the shells cost twice as much.

I guess I'm cheap.