Now we just need to convince International Outdoors to sell us some 20700 tubes. With knurling. 
Happy belated DB
Uh, well…. I got the D4 bored for the 20700. (first time to work on the lathe after surgery, it’s 104º in the shade, no air movement at the lathe at all)
Even using the Sanyo “B” cell it’s drawing 19.54A at the tail! 
In case anyone’s interested in more theory here, here’s a rough comparison of FET + 1 vs a FET + 8 + 1 driver (numbers from a quad 219C D240):
At 1000 lm:
1000lm / (300 lm / W) = 3.3W
FET + 1: Efficiency of 64 lm / W > 1000 lm / (64 lm / W) = 15.6W - 3.3W = 12.3W of waste heat
FET + 8 + 1: Efficiency of 113 lm / W > 1000 lm / (130 lm / W) = 8.8W - 3.3W = 5.5W of waste heat
That’s LESS THAN HALF as much heat using a FET + 8 + 1 driver.
At 1400 lm:
1400 lm / (300 lm / W) = 4.7W
FET + 8 + 1: Efficiency of 82 lm / W ==> 1400 lm / (82 lm / W) = 17.1W - 4.7W = 12.4W of waste heat
If a FET + 1 driver was thermodynamically was stable at 1000 lm, then a FET + 8 + 1 driver should be stable at 1400 lm.
Any pictures of your setup on boring it? I recently got a lathe and need all the ideas I can get!
Might need to customize the firmware. All excessive current problems could be easily solved if you could limit the maximum output to, say 70% max FET.
Even better would be if the user could manually set the max turbo setting, like can be done with the H17F.
I hadn’t used my lathe for months, slipped 2 discs in March and pinched the radial nerve in my left arm, had surgery June 22 and am still under Dr.s orders …. I asked about operating the lathe and he cautioned me to watch for issue and stop short. That said, my lathe is in a 44 year old shop that’s attached to a barn, it’s filthy in there! As a photographer, my gear don’t go where the lathe is! lol Sorry.
Just used a boring bar and made small passes, kept it to what would just allow the Sanyo B cell to fit, Efest high discharge cells won’t go in it. I wasn’t thinking or I wouldn’t have started it. The longer cell needed a spacer between the tube and head. This removed tube contact from the driver, so I had to put solder blobs on the driver ground ring then file them to clear the fat cell. Also had to remove the spring from the driver. And then I had to address the tail cap, solder blobs around the ground ring so the tube would contact. The spring is pressed flat, it’s a very snug fit without going to greater measures. I made a copper spacer ring on the lathe so I have a shiny copper ring between the head and tube on a green D4. 
And as it so happens, the B cell I put in it for the 19.54A reading was at 78% charge level, so … charging it and will get a new reading, try to get a lumens reading, but am heading out to a rehearsal tonight for an event tomorrow… might be a couple of days before I can get back to readings…
Once again I’m in a position of not understanding.
I charged the B cell up and tested with my bigger clamp meter, 12.92A at the tail. Tested again with my smaller Uni-T and got 12.32 (falling, hit on the cell) Then I stuck it in the light box for a reading of 3657 lumens at start, falling.
I have no idea where or why the previous 19.54A reading. Not sure how I could stuff that up, but there it is.
Sorry about that. I find it kind of nice sometimes and kind of annoying at other times. With no clear right answer, I left it as-is. It’s easy to change in the firmware though, if you want.
I wasn’t really expecting this thread to hit four digits. It’s not a big long group project like the Q8; it’s just a review and a few days worth of development. Was planning for most of the discussion to happen in Hank’s D4 thread, but he was having difficulties with the Great Firewall of China and couldn’t post for a while.
I really appreciate the feedback everyone has given though. At least half the things I changed were because people made requests. Like, I hadn’t really considered adding a channel-switch blink, but it was a good idea that I find useful.
As it turns out, I’m in the middle of building a color quad light… but not with a FET. It’s using a dozen 7135 chips instead. It’s only 1A per emitter, but that should be plenty for my purposes.
I expect a FET might make magic smoke.
I’ve been meaning to measure that for, like, years. Thanks!
That’s kind of what the FW3A is about. The D4 might not have quite enough room (depth) for 7135 chips on the back side of the driver. It would be nice to have FET+N+1 instead of FET+1, but I find most of my use is on just the +1… so it’s mostly a theoretical upgrade for me.
I’m definitely not the type who goes through multiple 18650 cells in a single night. Usually it takes me at least a month per charge, even on 1xAA or 1x16340 lights.
I require higher illumination levels TK. I, unfortunately, don’t have the extra acute night vision of a not-so-minor deity. 
Remind me where you got the numbers, 64 and 113 lm/W?
Just received my grey nichia and wow. I’m new to the world of led flashlights and this covers a lot of firsts for me. First 18650 light, first quad, first pocket hot rod. This thing is amazing, it’s so bright it’s like having a little piece of the sun in your pocket - heat wise too.
It’s actually much smaller than I expected. I bought the 18500 tube for edc but don’t think I’ll need it.
I keep wanting to get one of these lights but the glued driver and pcb in the tail keeps turning me off.
The glued driver is easy to pop out… the tail PCB not so much. Basically, the battery tube is a giant retaining ring.
Fortunately, the tail doesn’t generally need to come out unless you want to replace it with a magnet like CRX did.
i bet you wanting more and more no stoping now 
Nah, it’ll probably be easier to not get sucked in, knowing that almost everything else will be a disappointment compared to this. There’s basically nothing on the market yet which gets anywhere near the lumens-per-cubic-centimeter ratio of this one.
Of course, you’ll still need a thrower… and a compact thrower… and a keychain light… and maybe that one with the magnetic ring… and that pretty copper light… and…
Okay, maybe rizky_p is right. You’re screwed.