Whats the largest grip out there? I have a Magpul MIAD on one rifle and I'm using the large back strap. I bought another MIAD for a 2nd rifle, and I got a dud grip- the hole for the selector spring was drilled too deep, so the selector did not stay in place. I'm returning the bad MIAD, and I'm open to suggestions on other grips for giant paws. If nothing else I'll just exchange for another MIAD. Thanks.