I have a DBT six mag pouch for the AR mags on the front. The pouches carry six mags (two in each pouch) with the flap covering them, but I tuck the flaps into the pouch and use them as open top singles. For 1911 mags I like the DBT open top pouches with the magnetic retention( detloc I think it's called), and those are on my left side a little farther forward than where I keep the mags in my kydex on the belt. I'm not a fan of stacking mags on top of other mags as it tends to get a little heavy and bulky in that one spot. I prefer to have the weight spread out and lower profile. I also second the dump pouch being on the belt.
ETA: Diamondback isn't the only manufacturer that makes that style rifle mag pouch. Just about every major company that makes pouches has their own version of that particular style pouch.