Less than you might imagine. Pain in the butt to get the switches mounted 120 degrees apart on a 3 fin rocket (I use 3 holes on a 3 fin rocket, 4 on a 4 fin) UNDER the vent hole.
lol I do the same thing, 3 holes for 3 fin and 4 for 4 fin..if I ever make a 5 or more fin I may have to rethink that one otherwise the rocket will end up looking like Swiss cheese.
I have never used mechanical switches as I bought into the featherweight magnetic switch idea and haven't looked back. Having said that as much as I am confident in them, when it comes to my L3 I may opt for a screw switch. One thing I do on all my AV bays is to key them which makes lining up the shear-pin holes a snap.
I do own a few 110/220 SCHURTER switches, as well as screw switches and even the snap action switches, but I have yet to use them. I even contacted an inside sales rep at SCHURTER, Inc. to find out if it was possible to have a custom legend (safe/armed) printed on their switches but the min quantity was 5,000 plus a set up fee, which I never asked about.