I think this is the driver in the L5
Edit: Here is an HKJ review. Looks like a 20mm contact board mated to a 18.5mm driver. Probably too big?
Edit again: Does anyone have a source for” this driver”:http://www.fasttech.com/products/1612/10001753/1127409-3v-8-4v-5-mode-0-7a-led-flashlight-driver-circuit? Check out the reviews and the Fast Tech results on the linked page. Looks like their getting 3A with 2 lithiums, even though it’s supposedly a .7A driver. I can’t find a source for it though. I’d love to get a solid 3A in a 17mm package that can take 2 lithiums.