I just used an old 2-AAA minimag tube that I cut down to fit. It's not threaded and doesn't fit very well so I just put in a couple of batteries and used duct tape to hold the mess together for a test.
I didn't do any formal output tests, just eyeball and no runtime either. I was just trying to see if it would work.
On Alkaline it works fine - levels all work and it's got solid punch. The batteries hold up well, I can't see any difference between alkalines and NiMH cells.
On Lithiums it seems about the same as running it on a 10440, same slam of light, too much really, the head got real hot real quick, it obviously wasn't going to take it very long.
On NiMH cells it ran just fine Great output, no overheating like it does on lithium or a 10440. Still gets quite warm on Turbo but not like lithiums. I only ran it on Turbo for maybe 10 minutes but I'd guess the temp had stabilized by then. This seems like the best combination.
Low and medium don't seem too different from single AAA, a bit brighter across the board perhaps. High seems about equal to my P1D, the advertised output of a P1D is about 70 lumen's.
Turbo really jumps the output, I've no way to measure it but there's a considerable difference.
I've been trying to have a tube made to fit at a shop near me but they seem to be having trouble finding the right material for the tube and even more trouble with the thread pitch on thin walled tubing. Their not particularly interested and are just giving it a try because I asked.
I've also considered using the battery tube from my older L0P and have it mated to the L0P CE tube at the machine shop, they said they could do it so I might go that route if nothing else shows up.
Al