Whitedoom, just responded to your similar post in the P60 thread.
To everyone else here who has recommended a metal head for the G2 as opposed to an all-metal light for continuous runs of high-power drop-ins over 15 minutes or so, here's a simple question: Do you have any evidence to back up the implicit claim that this solves any thermal issues that might crop up?
I'm just curious. Granted, as long as the OP doesn't use his light as a candle on high, heat will never be a problem. But what do you all think about the issue in general? As far as I know, chevrofreak hasn't done output/runtime tests yet on any drop-ins with nitrolon bodies and metal heads. We can assume that if SF went this route, there's some benefit, but that's with a drop-in that is significantly less powerful than the WE drop-in that the OP mentions.
In order for the head to make a really big difference, there would have to be good contact between the drop-in and the head (right?). Is this the case for a G2 with an aftermarket drop-in? I've got a WE drop-in in my G2, and the only contact I see that the drop-in definitely makes with the light is (a) the thin contact spring touching the inner metal tube in the body of the light, and (b) the front of the drop-in resting on the glass/lexan lens. My Malkoff drop-in seats in (and makes contact with) the head much more significantly.
Anyway, I tend to think that if one is worried about heat, an all-metal light would be the best bet. Buying a relatively cheap metal head that's not guaranteed to be effective in managing heat may end up costing more $$ in the long run if the drop-in has to be replaced, no?