If you assemble the switch with the bottom contact screwed down tightly you aren't going to have an issue with the pin falling out. The bottom contact is not a throw adjustment, if you want a shorter throw you reduce the delrin ring height or use a longer rice pin (which at some point will require a longer contact screw as well).
Maurice
I hated my Nemesis(s) until I had that revelation.. Once I got them right they have been awesome, at least for my wife and I.