Yeah, maybe, mostly it's just different. I find I use it in momentary mode most often (and I prefer forward clickies anyway, so it's not all that different). But look at this...
I mean, those are both 16340 lights!
Pretty neat there Comfy! You’ve got it down to an absolute minimum. Now you need to make 100 more for a group buy! 
100?!? LOL! :Sp
It looks like the XIOwhatever/X-Power/D4 would be the easiest to shortify, from the pics I was able to find the threads go nearly all the way up to the front end. But I've never handled one in real life. What's the quality like?
Is the TR-801 really too funky/ugly/different to the point it would turn people off? I really like it, after the silly strike bezel is chopped off it feels like a totally different light. The anodizing is also really really good, especially for being a lighter color which usually ends up more fragile. I don't have to take any special precautions when abusing the parts on my half-assed drill press. I've even had a few slips with the diamond files and they come through with nary a scratch.
Really my main sticking point was drivers, or more specifically driver firmware (lead time on the 3XP boards themselves is another issue...). But I just double checked the NLITE page, and whaddya know, it says "it's completely free (including commercial use)".
So, should I start a 'feeler' thread? Keep in mind these come in at something around $35-38 just in raw parts, would anybody really pay $50-55 for a little pocket light built around a $10 host?
I have the D4 in stainless steel (actually I have the Convoy S7, but its the same host), the threads dont reach up the head far enough. You'd still need a 6mm spacer. Or remove the threads of the pill, but that might end bad because its only 9mm high in total. Other than that, quality is really good imo.
And yes, I think the TR-801 is ugly. :D But it seems to be one of the few lights that can be shortened that much without access to a lathe.
And now i’m looking at aluminum round stock on Ebay….for my S3….ugh….I already have a Triple…but it’s a Nichia…
Maybe it's just the angle that makes them look different, I don't know. Compared to the Convoy S2, where only half the head is threaded, it's a huge difference.
On the S3, I think it's easier to move the driver rearward (like I did, using a P60 pill as an extension) instead of using a spacer on the top.
I'm sure someone on this board has that host and I can make some measurements. :)
But I'm pretty sure it's just the angle, sadly..
What if it were stripped and re-anodized black? Though I seriously doubt I could get a finish at home as tough as the original silver...
BTW, here's what you end up with if you ditch the glass lens (and shorten the front of the pill a tad):
Convoy S2 head is 1.740" overall, and there's .800"(!) of unthreaded dead space in the front half!
I actually dont like the overall look of the light, not really a matter of color. I dont know what it is though..
How does the optic stay in place then? Is there a lip? Thats the problem with most lights you could cut down - no way to fix the lens after that.
/edit: 0.8".. that is 2cm or 20mm. :P On the D4 (stainless) its 16mm.
Yes, the lip is still there at the front (though greatly enlarged over stock, not wide enough now for an o-ring). Just the pointy bits were cut off the front, then cut at the other end to shorten. Both these lights were built originally for a different reflector, I would do them slightly different for the 3XP/TIR if starting from scratch.
Those slots are why I want this as a host.
V10 Ultra glow + Devcon 2 ton and slots are filled with nice glowy goodness. Plus the extra space will allow me to put a plug of copper in there and shift the driver towards the head slightly to allow protected cells to fit.
Fingers crossed it all works out.
EDIT:
Thanks for posting the picture of this host with the 3-up board and optic installed. I wasn’t sure how it was going to sit.
Hey Comfy, what’s the overall length with it in shortest form? What power level would you be running it at?
I bet you could sell some, maybe not 100, don’t know. But you just can’t find anything that size making that level of out the front power.
My chopped AA minimag should be here today, I’ll see if I can fit my pill into it and perhaps it’ll run at around 1000 lumens at 3” or so total length. Might even shorten it more with a tailcap clicky. 
I have and reviewed the D4/Xiozhi/X-Power light.
That’s what I mod for Nichia triple. You can find the spacer measurements I talked about on previous pages but once again minimum is 2.5-3mm spacer and maximum is 15.5mm.
The threads don’t go far enough without using extra glass or something. So you do need a spacer below the MCPCB. I use copper that I have.
Don’t buy from fancyflashlight as their tails have too high button cap/boot what ever it’s called the green silicone button. And the PCB of the switch is too small. But you should be fine from FastTech or elsewhere.
The light is in parts so ask away if you need some measurements.
I have Carclo 10507, the narrow clear and alu MCPCB for testing before Noctigon arrives.
I used protected and buttoned battery and Nanjg 105c for measuring.
I did cut, sand and polished the pill so it can take 20mm boards or a 20mm spacer instead of 16mm.
Having tools, this is not hard to do, people might like it, but then again, you need tools to make things like this. Well equipped garage or some shop especially if cutting it shorter.
1 piece ok but doing 100 pieces is a little different.
And the total price does add up, $10 host, $3 MCPCB, ~$15 for emitters, lens, o-rings if they need to be added or changed, $3 driver + soldering if you want more output which it can’t dissipate though (2A is enough heat for this size of light), cables, …
Material, cutting, other work, …
$30-35 in material easily as you said + work
I like the D4 and am looking forward to using it again instead of UF C20. Triple Nichia 219, still thinking of direct drive to avoid the 0.1V drop on AMC7135s. Can always limit the output by PWM modes.
D4 has 115mm, realistically 116mm due to tailcap not screwing all the way because of the switch assembly which is very compact and uses low profile boot. But if you want it to tailstand it has to be done well and the boot not pressed out. On mine the boot goes out a little due to compressed air inside when closing the light, which goes away after some time when the air leaks, slowly. Stands fine. You can see that on FastTech that the tail does not screw all the way down.
In my setting when suing Nanjg105c, Carclo lens and O-ring, I could take away 12.5mm from the length due to more compact head assembly. So you’re looking at 103-104mm or so total length with tail clicky.
The front rim does cover the lens a little so the lens or reflector holds inside, this happens on all lights but it may be less on some or if you increase the id/diameter in front of the lens.
No idea how much you would reduce by removing the tail clicky and making it a twisty.
My guess and measurement is possibly getting to 94mm still with protected battery of 70mm.
DQG is 90mm but won’t fit protected batteries. Sure you could get smaller if you’re willing to give up some things and milometers of material that make the light strong.
Easier it may be, but I want to “try” and make it a tighter fit for there to be more surface area for heat to transfer to the body…Winter is Coming…need to keep my hands warm somehow.
@JackCY: so you need at least 3mm of spacer if you keep the lens in front of the optic? Doesnt sound like too much. And then you would chop off a part of the head, have to remove the threads because of the O-rings and thats it? Doesnt sound too complicated. Most Dremel bits (the tough ones made of steel) will remove aluminium, you could even use the round sand paper, would also work.
With the shorter no-lens head and the tailcap unscrewed to the 'off' position (off, but not far enough to be locked out totally) overall length is 3.7", or 94mm. DQG 18650 is listed as 91mm, but it also doesn't put out ~1500 lumens.
I can make this fit 70mm protected cells, too, by moving the driver forward in the pill, which won't affect the outside dimensions at all. There's plenty of space between the top of the driver and the bottom of the new forward-mounted LED shelf even with a triple stack of 7135s.
12x 7135s is probably about right for the Nichias, 14x for the XPG2s.
If my only option was to make an o-ring counterbore with handheld tools, I wouldn't bother. I'd leave the threads as-is all the way down to the cut line, use the light long enough to know everything was working as it should be, then seal it with a little clear RTV silicone on the threads. Honestly, how often do you need to disassemble the head? And when you do, that stuff peels off pretty easy and is easy to reapply.