Thank you, Terry. I decided for now to use the Silver 10/20 inserts, since the Silver 10/12's are slit and the Gold 10/12's are a little out of budget after what I just paid for the shotgun and a flat RST ammo. I contacted several ammunition makers, and none of them would reveal pressure specs of their 2-3/4 loads beyond "we don't exceed SAAMI spec", so I decided it best to use the thicker, solid 20 gauge inserts.