I think it is relatively easy to modify mag capacity, but jumping the legal hoops complicates things...like it always does. A wodden or metal spacer is the easy way, which is legal in shotguns, but I think the rules are a bit more stringent with high-capacity mags. It may very well depend on the attitude of the game warden you happen to bump into that day. Canada allows mags to be modified with a pop-rivet. Only drilling a small hole thru the housing and snapping-in a rivet is about as easy as it gets, save just dropping in a spacer. Good Luck!