Added tailcap measurements to OP.
Really nice job RMM! Hhmm - like that C8 extension tube, for $8 shipped from US, not that bad really - it's an unusual item. I didn't know they were available.
Great mod RMM! One of these days I'll do an MT-G2 build!
-Garry
Thanks, I just saw your post. A little pricey considering Banggood just had a whole C8 for $8.88, but what can you do? 
Great mod! They way you do this is quite clean and thorough.
Thanks for the comments!
You’re right, $8 really isn’t that expensive but it is hard to swallow when you know that you can buy entire budget lights for less than that! 
He doesn’t have very many left, so if you are interested in one it might be good to pick one up. The anodizing isn’t perfect, but it is good enough and the threads are good.
I have debated cranking up the current on this a bit more by adding a few more 7135s but I think I’ll leave it as is for now. On one hand, there are three lower power modes that are very usable, an MT-G2 deserves to be driven hard, and high could function as turbo mode that only sees limited use. From what I’ve seen, think that I could see 6 amps on these cells with On the other hand, I think that 4.5 amps puts out a good amount of light, doesn’t slam the batteries too hard, and can be run for 5+ minutes without getting too hot to hold.
The thing that has surprised me the most is that this light has quickly become my favorite all purpose light for use around the house, and it now resides on my nightstand. The wide, smooth beam pattern and attractive tint make this one a winner. Moonlight is nice for getting up early in the morning and during the night without disturbing anyone, low provides plenty of light for completing tasks in the dark, medium lights up entire rooms, high is just too bright for anything too close but is great for wide open spaces.
This thing isn’t a great thrower (my XinTD V4 and ZY-T08 are better at long range), but it is a great light for everything else.
Nicely done! I know you’re loving it, as I love mine. I have an MT-G2 on a Noctigon coming my way, with a Qlite already modified and waiting, to put in my M8. Already tried the hybrid reflector on the light engine in my K3 and the beam is very satisfying to me, so I’m very much looking forward to my 3rd MT-G2 light.
I haven’t chosen star 4 yet, but your work here makes me think I need to. Might do that to the M8 and expand it’s horizons. 
Thanks for that tip.
When you get ready to really put your mind (and hands) to work, figure out how to add some copper to pull the heat away from that monster, you’ll see your run times go up!
I really like the fourth star on the Qlite… but I realize that it may not be everyone’s cup of tea. The good thing is that it’s easily reversible/changeable if you don’t like it.
I’m not sure that adding a little bit of copper would really extend my run time by much. I thought about putting some in the back of the pill behind the star, but really all it would do is add a tiny bit of thermal mass, not aid in removing that heat. The pill is large enough and has good contact with the body and fins, which heat up fast telling me that they’re doing what they’re supposed to do: remove heat away from the star/driver. I am building a ZY-T08 MT-G2 right now that I’m going to try for maximum amps on… then I can compare the two.
I’m not talking about a little bit, more like several ounces. It does much more than add a tiny bit of thermal mass.
Mass isn't a magic bullet that makes heat evaporate or teleport into a parallel universe.
Tell that to the Elephant taking a 300gr .454 Casull in the brain.
Edit: A rogue Elephant that had been rampaging villages and killing men, women and children happened into a village where there was a hunting guide. Not having his rifle handy, he shot it with this very powerful handgun. Dropped it in it’s tracks, effectively dissipating it’s heat with a little bit of mass. The villagers treated him like he was a god.
That said, if mass isn’t so critical, why is it always at the top of the list in the most powerful lights? It might not be magic, but you don’t get far without it.
Apples and oranges. Let’s keep this friendly!
If a pill is thin under the mcpcb and having a hard time transferring heat to the rest of the pill, then maybe adding copper under the mcpcb would help.
Adding excess mass does nothing to solve the thermal problem if it’s not getting the heat out to where it can be radiated to the air. Surface area is really what would help in this case, but then you lose the benefit of the small light. (same goes with adding unnecessary weight)
I think that's true for continuous run times, say >10 min., but many people use a turbo mode for 30sec to a minute, then have a light off or on low. Then a massive pill is a thermal analogue to a capacitor in an electrical circuit, quickly accepting the heat from the led on high to be dissipated more slowly when off or on low.
The differences between playing with a light and working with a light I suppose.
When a storm knocks down a large tree that has to be cleared from the road, or a fenceline, and it takes an easy hour to do, you don’t want your emitter sliding off it’s star. When your $600 pedigreed pup gets under the fence and is lost in the back 40, you don’t want to keep shutting the light down so it can cool while you look for the poor guy.
But I hear ya. Always a compromise, as with so many other things…
I thought this thread was about a fun pocket light, more than a heavy duty work light.
So... should I shoot an elephant to keep the light cool, or shoot the light itself? I can see how needing to find an elephant to shoot every time you want to use the light could be a little inconvenient. Shooting the light would definitely reduce its heat output dramatically, but I think it might have a detrimental effect on the runtime. I will need to do some further research on this, but thanks for the tip, definitely sounds promising!
No, train the elephant to hold the flashlight in it's trunk, the elephant is the heatsink.
And then you shoot the elephant? I'm very confused.
The question was one of mass not being the magic “bullet” which made my feeble mind remember a story about 300 grains of copper mass indeed being the magic bullet. So, relevency being the key without getting further off on this tangent, mass is of course crucial to keeping heat off the emitter. Be it added copper or thick aluminum construction to begin with. The light in question was not designed for the wattage that is being put in it, so I suggested added crucial mass in the most effect composition commonly available…copper.
Go ahead, put an MT-G2 in a Xeno E03, whatever. Just because you can, doesn’t mean you should.
Shoot the shi*, feed the elephant, build the light.