I've had two of the G&P 3W modules. When they first came out, you had to specify that it was to be used in a G2 vs a 6P. With the G2, it came with an extra spring. My first module was straight from the factory and it had the extra spring. It worked fine and I never tried to use it without the extra spring. The second module I got was actually modded by a member with a TW0J (or maybe a TW0H) and it came with a Maxfire and did not have the extra spring. That module also worked 100% fine without the extra spring in both of my G2s.
A bit later, I got a Vital Gear body for that module and it got a bit warm when run on 2xR123 cells, but stayed perfectly cool with either 2x123 cells or with 1 17670. I'm not offering it as advice, but I think the 1W or 3W is fine in a plastic body as long as you don't run it with R123 cells.