Shadow S-L3 has one disadvantage - the long running 30% “mid” mode is only about ~870 lumens which is almost the same thing as regular 1x XML2 18650 flashlight (and hi mode works only for few minutes).
Something that has better, long running, “mid” (like 70%) mode would be nicer.
The MMU-X3 is a special light no one seems to have cloned, or even reproduced in function and form factor. I would think it's impossible to get 2 hrs and maintain 1600 lumens, because the draw on the cell is like 4.5A - 5A, so don't believe that spec. There's probably a kick down built-in in either time or heat - specs say it has thermal management.
There are smaller options (DQG - but with XP-G2's - less output) and several bigger options (Shadow SL3, SRK's, etc.). There's probably some customs out there that do it, but wouldn't be cheap - think there's been custom builds in the P60 form factor for triple XM-L2's.
It's not rocket science to build triple XM-L2's running parallel off of one cell, but the package and reflector must exist.
Interesting... The SingFire is bigger all around in size and weight, has only XML T6's, but it's closer for sure than any others...It's also probably well under driven because they wouldn't put in temp monitored regulation in a cheap light.
The MMU-X3 does indeed step down after a few minutes in most circumstances. But the stepdown is thermal rather than a dumb, timer-based stepdown. As a result, the amount of time you spend at 1600 lumens depends on ambient temperature. So if you’re doing a nighttime walk in mid winter, you will likely get a nonstop 1600 lumens. This, of course, will give you much shorter battery life. When the light DOES step down, it steps down to around 800 (or so) lumens.
BTW, if you’re looking for a light of this size with no stepdown, it’s unlikely you will find one.