Need someone(s) to share their experiences with a G2 and Li-Ions

I recently scored a used but very good condition Surefire G2 on eBay, and replaced the P60 with one of Lumens Factory's XP-G tri-mode drop-ins. Very nice combination, I'm very happy with it. But I am getting low on lithium primaries, and don't really want to buy any more. From my research I have determined that RCR123s, a 16650, or a 17650 will all fit in a G2. What I would like to hear are peoples' experiences with doing that, and how well it turned out for them. I am not concerned about the drop in, as it will handle 3.6-12v easily. Anyone willing to share?

Did you search for similar threads? - Norm

Yes. But most of the ones I found were old, from before Li-Ions were popular.

I have three G2s, one LED (KX4 head) and two incan.
All of them fit 17670 and 16650 cells perfectly. I am partial to the 16650s now because of the higher capacity2000 vs 1600 for the 17670),.
I have since managed to burn the SSC P4 on the KX4 head(left it in for an hour). SF replaced the head, so I squeezed my Malkoff M60 on the KX4 bezel after gutting it. Two different G2leds for me now.