Nice pics and collection. I would like to have one too. And thanks for the measurements.
BTW recently watched maglite mods 
Here’s the effect the lens has.
Transmission: 98.4%
Without it the beam is a bit rosier (duv –0.0030 vs. duv –0.0018).
With
Without
A relatively small change, but I’d probably like it better without the AR lens. A bit closer to my ideal CCT, with a bit of extra pink, is a double win.
The difference with vs. without lens is practically imperceivable with a CIE 2000 deltaE of 2.2. Everything under delta E 3 is difficult to notice with the naked eye.
Really good review, thanks maukka :+1:
Awesome review!
Glad I ordered the Nichia version and not the XPL HI version.
Excellent review once again! Think I do have a potential fix, can't be sure but potentially. I'll be talking to them today.
Still wondering about the lumens. In theory this light should be equal to 3 triples, 1 batt per 3 LED's. I don't know how the path from the LED's through the battery is, ex: thickness of LED wires, etc., quality of springs, but if an equally tested 219B triple could be tested for comparison, it would be nice to know.
3860 lumens means 429 lumens per LED, or 1287 lumens for a FET based triple.
I only happen to have an Astrolux S41S with 219B sw40k R9080 and MTN17ddm FET driver with bypass on the driver and double springs in the tailcap. It only does 900 lumens max (at 0 sec) with a fully charged 30Q.
edit: another point of comparison is a triple 219C R9050 BLF X6 with a FET (h17f driver), it does 1620 lumens at 0 sec, 1560 lm at 30s.
That's interesting, not the same LED's but big difference per LED.
Thanks Maukka, great review as always.
At 65 degrees, is it still possible to hold the flashlight?
Found another 219B triple, edited my previous comment.
edit: and realized it is actually a 219C CRI90 triple…
Nice review, thanks! 
65°C was at the head, it takes time to travel to the rest of the body. 65°C is too hot to hold, about 50°C is what I can handle for a short while.
Thanks Maukka
Fireflies mentioned larger domed LEDs like LH351D would not fit. Is this true?
What a review, great
Thanks for this great review, maukka :+1:
Just wondering why my ROT66 could stabilize at ~700 lumens with a temperature of ~43°C (at the head) after hours of testing. I tested it under a 25°C room environment. One possible reason I can think of is, whether the runtime curves are measured directly with a integrating sphere or not. With the sphere attached, the light can heat up noticeably more quickly, so I used to measure this with simple ceiling bounce (and then apply an appropriate multiplier based on the integration result, of course). I may test again once my replacement ROT66 come back to me.
In the runtime test the head isn’t in a completely enclosed space, but I’ll check the temperature at 700 lumens with the light tail standing, thanks for the observation.
Can’t match your results even with a better environment for the convection to take place and without the initial turbo heat buildup.
At 26°C room temp on the 7x7135 mode the head heats up to
45°C at 15 min
46°C at 20 min
49°C at 25 min
50°C at 30 min
52°C at 35 min
53°C at 40 min
It will probably still be handholdable indefinitely taking into account the heat sinking from the hand. Especially outside. So that’s a great choice for the number of 7135 regulators in the 219B model by Fireflies.
Interesting. Sorry that I forgot to mention: I measured the max temperature around the side switch, not the SS bezel. This is because the hottest part I may touch is simply around the switch. I’ll confirm that again once mine is back.