I just ordered a Condor Kangaroo Triple Mag Pouch for my new plate carrier. The Kangaroo should MOLLE to the new carrier, and it has pouches for three AR mags with pouches for three pistol mags on the front of the rifle pouches. In theory it seems good, maybe not idea for trying to get really low in the prone but I don't really plan to run-and-gun while wearing my armor; it's more intended for HD use. I plan to look into a pistol holster that would attach to the top front of the carrier but I'm not sure yet.
Also about half an hour ago I ordered a GG&G sling attachment device from Midway for my Mossberg 500. Recently I bought a Streamlight TL-Racker WML forend for the 500. It works well but now I can't really use the sling stud since it's right in front of the light. The GG&G product moves the sling up a couple of inches and over to the side by an inch or two which should keep it out of line with the light.