Hi Paulr,
Ah, I didn't catch the part about where the light was going to be used. That considered, I agree the MM+sandwich is a bit too fussy. In fact, I think the MM would be too fussy.
With this new understanding, I looked at the PT, UKE and SL again (since I have them at hand).
I would probably select the PT except it uses a dinky O ring. I think you'd really want a bit more heavy duty seal.
The SL 4AA 7LED has a slightly larger O ring, but still not as good as the UKE lamp(s). The flood is very useful for close up stuff and the switch works easily. Probably not a bad selection.
The UKE has a much better O ring than the others and feels a lot smaller in the hand. The thing that is annoying is the switch. It is very stiff with no feedback. The other thing is as you pointed out, a switch is something else to maintain. So... I'm thinking a MiniQ40 w/eLED module. The other thing about this is the Q40 moves the O ring farther forward and omits the vent. I'm thinking both things would help add a bit to the reliability.
I'd also consider (As Paulr also recommended) the CMG Infinity Ultra or Infinity (regular). Certainly if I was traveling to such a place this is a light that would be on my must_take list.
Gman, I would consider what Paulr said about the Kroll switch. I have some and while I haven't had any problems, they are cheapo plastic thingies and I wouldn't put them in a critical light. My understanding is the Jr uses this switch.
Also, I wouldn't consider the MM (even w/o the tailcap) for this kind of duty either. It's got a lot of parts and isn't super waterproof. If I did take a MM in this situation, it would be with a Newbeam which would give decent runtime with the batteries available.
So, all considered, I would recommend the UKE MiniQ40 w/eLED and a CMG Infinity.
Sorry for the ignorance, but what does CIS stand for?
-john