I've done several glocks, 1911s, etc with the lower rail. Heck, my Springfield has one and that holster is worn a lot, and shows little signs of wear. When I wet mold them, I move them in and out several times. It loosens them up around the lower rail (I hope that's what you are talking about) and I see no signs of significant abrasion. I get most of my retention from the trigger guard, ejection port, and sweat guard.