How does the round side mirror attach to my '71 S2? Cursed stem is loose and won't stay in one place. Went out tonight to remove it and tighten a hopefully existent spring tensioner under the ball, but the screws holding it onto the door only loosen slightly; I can turn them all I want and the mirror isn't coming away. Is there a nut underneath (meaning I need to pull the door panels and vapor barrier off to take the mirror off)? Not something I should have started at 11:30 at night; at least I knew enough to give up for now before I break something.