Hello, i modified my Maglite Ml50l to use a single 18650, but I don't know if it's absolutely safe. The maximum discharge or amp draw rating of my battery is 4 Amps, but I don't know how many amps my flashlight pulls. I don't have a multimeter or money for one. I imagine that the ml50l would pull around 2.2-3 amps? Just a guess.
If anyone is wondering, the ml50l uses 3 c cells at 1.5 each comes out to 4.5 V, but I retrofitted my flashlight to use a single 18650 that runs 3.7 V to 4.2 v. So far it doesn't get hot but I want to be sure.