I bought a couple of masonry bits- one a little larger than the shaft of the MAG nails I was using, and one a little larger than the head- and, with a rechargeable drill, drilled a hole deep enough that the nail would drop into it and be flush. I then put enough glue into the hole that it oozed out a bit when the nail was dropped into the hole. It'd take some serious effort to dislodge such a nail.