I usually place them on the side toward the rear just below the level of the grate, that way a really hot fire will not have the chance to trip the switch by accident. On the Magnums the back wall is the hot air jacket so not really a great place to be drilling holes!
I've installed them on around 10 stoves (Harman, Alaska, LL, and Keystoker)) and so far no issues with placement. I just use a bi-metal hole saw to make the hole and use the gasket supplied with the switch or some RTV if it is a used switch for sealing around the switch tube.. I would test it after installation to make sure it shuts down the stove when draft is lost.
Best of luck with your search.