Nice. I think to start I’ll power the MT-G2 from two 26650, which can easily handle the amperage, and run time could be better than with 18650’s. AW or Panasonic can handle the amperage, especially 4 amps, but many 18650’s other than IMR cannot do so well, and efficiency is not so good. I am ordering some sinkpad boards for the MTG (as well as the XML), when I find time I will make a flashlight with the MTG2, two 26650, front switch. I have some 30mm optics I want to try out, and if they work as well with the MTG as they do with the SST-90 then the beam would be pretty good. I will start a different thread for this new flashlight though.
Even though the LED and sinkpad might be able to handle the amperage, eventually the heat has to go somewhere, and that means lots of heat sinking, lots of mass and surface area, otherwise, the flashlight will get too hot to hold, and also not good for batteries to get that hot, not to mention, hard to hold onto. 
Wayne