The regulations I have seen mention disassembly of the gun to get the plug out so with the trouble of taking of a magazine clamp to get the plug out you should be just fine. Be sure you can't put more 2 3/4 shells in the magazine than what is legal for where you are. Don't just take two shells and cut your dowel that long. I have seen wardens with gee whiz shell counter devices they love to put in your gun. Having an extra long magazine tube is going to attract their attention if you are ever checked even though you have it properly plugged. There was a thread sometime ago about plugging 3 1/2 guns and somehow when wardens put in 2 3/4 inch shells people got in trouble because the plug would allow one to many of the shorter shells.