Plugging aerial hole when removing radio? What did you use?

Cut a piece of 1/4" aluminum 1/4" larger than hole , drill hole in center for a #10-24 stainless cap screw . Cut a second piece in a rectangle same size but narrower with a hole in center for the #10-24 . Cut a piece of rubber roofing larger tan the hole but smaller than the first piece of aluminum . punch hole in the center of the rubber . push cap screw through top piece of alloy and cap screw . send cap screw thru second piece of alloy . Insert bottom piece of alloy in fender hole , turn 90* , tighten cap screw , snug not hard . You are done , watertight , polish to luster if you want . Materials <$2.00 , Time 1 hour tops