Thanks for the clarification Comfy! 
According to the Cree documentation, the MT-G2 at 6.0 forward Voltage, will achieve about 2200mA. I would use their information, as they are the mfg of the led.
Just FYI
I'm aware of that but the measurements in the real world disagree, I don't think it would be wise to discard things I've seen with my own eyes in favor of something published in a spec sheet.
You could try your hand at BBC fins writ large. Bore the head, cut behind the bezel threads, and insert your copper fins of frozen wonder. It’s a pretty cheap way to up the ante on a mag head. Having seen your other work I’m sure you could do this.
Yeah, I was thinking maybe just create a finned copper extension for the L2 that fills the head and spills out the back. Make it long enough and add another cell if he wants. Put a warning sticker on it for the heat! 
Ah, but…the L2P host has an enlarged area about 1” deep at the end of the battery tube to accept a P-60 drop-in. This area is where the copper heat-sink/pill will be. The outside of this area is threaded, to engage the head. The finned area of the K3 head that starts at or slightly above the emitter location is the inner threaded area such that the emitter is located in relation directly on top of the L2P host. Any fins added would be above the emitter and thus, less effective.
I could, however, sand out the anodization between the fins or otherwise contrive to remove it and then place copper into this exposed area between the fins. Does anodization stop heat transfer in a similar way that it blocks electrical transfer? Obviously it doesn’t block heat transfer, but does it reduce it?
I thought about boring concentric holes in the head, into the copper and pressure fitting copper rod into these holes as a pathway to air via copper. At the very top of the fins, where the vertical groove starts, this could be done. It would add 8 rods of copper, perhaps a 1/4” or 5/16” diameter into the mix and more importantly give an open via to heat dispersion. I can even envision these short rods tapping into the copper core being drilled and threaded, with a copper ring floating around the lights head anchored with brass screws. Like a teenagers retainer orbiting the head. I believe a gleaming ring of copper on the outside of the black K3 head would indicate something serious was happening inside. lol
That’s theoretical, as the only way I could achieve these 8 holes would be far from perfect. If my drill press were trustworthy it might be worth a shot, but it cannot be trusted to drill a properly centered hole, even with a pilot hole and extensive set-up prep. Now, there IS a machine shop just down the street. Like most machine shops, they’re expensive.
Aluminum is better at radiating heat into the surrounding air than copper. As long as the junction between the two is good a hybrid with copper core and aluminum fins will be better than all copper or all aluminum.
Thanks again, seems you’re just chock full of infinite wisdoms that get me closer and closer to creating bad-a$$ lights! 
Does the anodizing block heat release in any way? Would it be anything more than aesthetic to dress the area between the fins, strip the black anodizing and polish the space for contrasting bands?
Finally, someone that will agree with me on this point. I have seen arguments across the web about this particular topic.
I even got in the argument over at that other light forum on this subject, I eventually had to bow out.
They tried to say that the losses between the thermal path connections would be greater than if you had just made it solid, one metal. Even if a interference fit was used.
I have seen enough CPU heat sinks that where designed with a copper core and aluminum fins to know that its better than any one single material heat sink. These CPU heat sink company’s spend hundreds of thousands if not millions of dollars trying to come up with a better heat sink than there competitor. The heat sink that holds the lowest temps are like the Holy Grail with gamers and overclockers. They have used all sorts of design and different materials with some pretty expensive machining cost.
And after all that R&D they use a copper core with aluminum fins. The copper absorbs and the aluminum gets rid of it, the best properties out of both materials. What’s really going to be interesting, is when some starts using heat pipe technology in a flashlight. 
+1 mod and comfy on the copper core/alum combo. Interesting because that's basically what we are doing in the mods - copper star connected to aluminum pill and host, or maybe better copper star on copper pill surrounded by aluminum host. I'm still not sure how brass pills play into this, vs. aluminum, few opinions on it, but I think it depends on the actual aluminum and brass alloys used for the pills.
No arguement at all on those points just working within my own limitations. I don’t have a mill or lathe and neither does DBCstm and knowing this I first modded a light for him with soldered fins and was suggesting he try to do it now. It may be possible to use the same technics using copper core/spacers and Alu plates but I haven’t tried that yet but I can get much more surface area using thin cu plates than I can cutting grooves with a saw. We’re inching our way forward here. I’ll check the local scrap yard and see if I can find some 1 - 1.5mm Alu sheet and try a sample run soon.
-edit, maybe an old Alu cookie sheet though I’m loath to take one out of action.
Not long ago I bought 2 large cookie sheets as Sams for like $10. That’s a LOT of aluminum, and about the right thickness. Designed for it’s thermal properties and stamped as Professional cookware. Get a pair, use one, cut up the other. Simple $5 investment for flashlight aluminum.
The MT-G2 will take more heat than the solder that re-flows it to the star? That’s insane!
I have done that. Comfychair rightly already said it will take direct drive from 2 18650 cells, I posted the mod a while ago: link. When bypassing the switch the led eats 8.5A from two very decent IMR's.
I’d need a much larger host to relieve the emitter of it’s heat if I were to consider 8.5A!
Thanks djozz, I’ve been studying your charts quite a bit lately!
re: copper/brass/aluminum pill, the quality of the junction between the star and pill is likely more important than the materials. Brass might not be as 'good' as copper, but if you have a brass pill with the star soldered, and a copper pill with the star stuck on with Fujik or some other equally horrible crap, the brass pill will win. For an AL pill the best bet is probably a screw-mounted star with a proper thermal compound instead of any kind of adhesive or epoxy, no matter how fancy or expensive the glue claims to be. Copper pill with a copper star attached with lead-free solder and good thermal paste between the pill & light body would likely be at the top of the pile of course.
Not only does lead free solder have better thermal properties, its higher melting point means LEDs can be reflowed later without disturbing the pill-star solder joint. Plus, typical 63-37 solder paste has WAY too much flux in it for a large surface area joint like between a star & pill.
Anodizing does I think have a small amount of negative impact on heat radiation, but if the ano is black it more than makes up for it. Clear or light colored ano would probably be not very good and might show a small improvement if removed. But remember these are measurable but still tiny differences, ambient temps or wind vs. no wind will make much much more difference. 'Measurable' in this case doesn't mean 'big', just that you might be able to detect it with measurements.
This is all just guesswork based on how other stuff works, don't assume any of this couldn't be disproved with actual testing. :p
Even this horribly abused thing still works, electrically at least. There's just nothing to break like on the other LEDs - no skinny little bond wires, the dies are somehow a part of the base and not soldered like XML/XPG (I've had an XPG2 die lift off the base before, bond wires were still intact so I stuck it back in place with solder paste, and it worked again). None of the normal failure points exist with this one.
And yes, it's 2000+ lumens of very angry blue eye-burning light
Very cool 
I guess I noticed that the die was different, but didn’t put my finger on the missing brass wires. Very cool! The angry blue light, dangerously cool! Impressive findings and very helpful info on the pill/star junction.
I was planning on re-flowing the star to the pill and doing the emitter to star at the same time, applying some solder to the pads too while it’s all hot, would like to have the wires on there at that time but don’t see how I can accomplish that.
I do have one of TexasPyro’s re-flow masks to try out on the MT-G2, need some better solder paste though. I have some large diameter very old lead solder, should I grind some up and make my own paste? It’s probably acid core though.