The cup can be secured the cab, via short, self-tapping screws, from inside the cab, if you can contort yourself and the drill enough to drive them. Make sure they are, as short, as possible, to be sure they do not interupt the travel of the wiper transmission arms. Trying to do it from the windshield cowl cavity, may be a challenge, since you will be driving the screw through the fixed piece and trying to capture the loose cup, on the inside of the cab.
