You can, but you need an older Elzetta ZFL style. The new Charlie and Bravo with the AVS heads will not allow the use of the M60 module. The M60 is fully enclosed and sealed and slightly different than the M61s and M91s.
My understanding that Elzetta bought the rights to producing the M60 modules.
Nonetheless, both Elzetta and Malkoff lights are some of the best and strongest available!
I believe if you try to use the HL ring with M31, you have to start the light in a H mode for the module to light up. Once started, you should be able to switch to L mode.
But I believe you always have to start in H mode.
I have been using unprotected 18500 Sanyo cells for a few years now. No issues at all. I pay close attention to the cell voltage and keep the cells matched up. As soon as I see a slight output in lumens, I recharge.
I prefer the 16650 cells in my Bravo. They work fine for around the house...
Just a heads up on the bored Bravos. They don't accept all 18650 batteries, only the thinner shorter cells. I personally run Panasonic unprotected cells in mine.
But not all cells fit.
I also use the 16650 cells in my unbored Bravo. I actually like the 16650 Sanyo cells better.
I don't see why not. May rattle a bit. You really have to be conscious of the overall length of each battery for best fit. The 18490s are the best fit.