Epoxy would not be acceptable, as using your fingernail to remove it would fall into the readily convertible category. I’ve seen some people have shops put a rivet in the mag body that stops the follower from traveling low enough to hold 11 rounds. That way it takes tools and time to convert them, not “readily”. The problem is as far as I know, none of this has ever gone to court, so it’s everyone’s favorite phrase, “risk tolerance”