I'm stuck on a rock off the coast of France for a day or so longer. If you want to know whether you can remove the pressure switch the short answer I believe is no. You can remove the cover cap from the back but I seem to recall that the switch is soldered on.
The best people to ask are SureFire Customer Service.
I have an M115D at home (so I can check this at the weekend)
Sorry I can't be more helps.
Al