little food for thought...
a typical *large* format li-ion cell, like a 17670 or 18500 or 18650, into a 2 amp load (HO-M3T), can deliver about 4V fresh off the charger, so the lamp would see about 7.8V or so after resistance losses, diminishing to around 6.8V at the end of the discharge. Now... I would have to assume, that LF took this configuration into consideration when designing these lamps, considering the possible use in an M4 or leafbody... The lamps have a target voltage of 7.2, but LF hasn't updated their specification pages to include these lamps yet, so I'm not really sure what CCT and life rating the lamps are at when driven at 7.2V... one would assume, that there is some overhead in the design for comfortably dealing with the many possible configurations that could potentially deliver more than 7.2V.
Having said that, I think it's reasonably safe to assume, that the lamps can handle the typical output of a M6 style battery pack, (into a 1 amp load per cell, we could expect about 7.5V from the M6 pack into an HO-M3T)...
However... there is one small problem.. Fresh out of the box, CR123s have an initial "spike" of performance so to speak. Into a 2 amp load, CR123s almost immediately sag to ~2.6V each and then drop to about 2.35V within a few seconds, this is fine for the HO-M3T, it has enough overhead in the design to deal with these initial "spikes" because... if you do the math.. you see that the initial "spike" of 1 bank of CR123s, would deliver about the same as a pair of 18650s into that load.. However, and this is a big however, when you put 2 banks of CR123s in parallel, each cell is only dealing with about 1 amp, and that initial "spike" in delivery is much more dramatic, some brands will actually delver very close to a full 3V into a 1amp load for the first few moments in time, this is the moment that could be deadly for a HO-M3T, A fresh set of quality cells nailing it with nearly 9V.
So... that's my spiel on the subject.
Mark@LumensFactory has specifically stated that they do not feel the M3T lamps are necessarily suitable for the M6, and I would be willing to bet that his reasons are inline with my explanation above.... I think that it will probably work most of the time, biggest problem will be on fresh cells, especially warmer fresh cells.
All I can ask, is that the CPF community using the lamps in this manner be honest. LF has been kind to replace premature failures for folks here, please don't ask them to replace premature failures of M3T lamps that were subjected the the fury of the M6. hehe.
What we CAN do... is hope that they slap a EO-13 globe on an MN style LA, so M6 users can load up with RCR123s and enjoy guilt free lumens! hehe.
