Just did a bit of math 
First some assumptions, body shelf inner diameter = 70mm, 5mm overlap so emitter shelf = 80mm
80mm circle = 5026 square mm, 70mm = 3848mm, contact area is 5026 - 3848 = 1178 square mm
A 38.74mm dia circle is 1178.2square mm.
What that means is the heat path is the same as a 38mm dia light, and I have an xm-l2 t6 at 6A using less transfer area than that :bigsmile:
Cheers David
Ok, tried this:
Results: somewhat disappointing
4.2A tail reading, 547 kcd
This is a XP-G2 S2 2B de-domed, from an old batch at FastTech. Counting on the twisting of the XP-G2 to self-center in the XML size centering piece. Beam pattern didn't look too bad. As shown above, the centering piece was sanded on the top from 2.09 mm down to 1.76 mm. Didn't fiddle with any focusing, the hot spot looks pretty good, but there is some surrounding artifacts, but it looked well centered.
I didn't expect much with the 4.2A reading - not sure why it's so low. Was expecting over 5A. The tint looks good, the dedome seemed to go perfect, just a little silicone left around one bond wire. I got a dedomed V6 1A to try - might give it a shot.
Still need more time, but here's some notes on it so far:
Well it's one-of-a-kind. Not sure, maybe the largest stock light reflector? Certainly under $100 there is no comparison I would think. There's a bunch or pros/cons. It's certainly moddable, which is great.
If I can't get high performance from an XP-G2, it will be a downer, but if I can get a nice wide beam (well not really wide) from a dedomed XM-L2 or XP-L, I'd be happy, and should hit 600-700 kcd without crazy focusing. I was hoping for like 800 kcd, and still think it's possible, and that someone can achieve it, if this group buy can/will happen.
If the group buy happens for $50 or so, it's a steal to get this kind of size/power. Mechanically, I'm maybe most concerned about the driver retaining ring - I think it can fall apart being so thin, frail. I think the shelf is not such a downer. The wire clearances are always a challenge with this type of reflector design (way too wide bottom). I don't think the driver is that bad as well - it doesn't seem to have bad loss's with mods, least what I seen with the XM-L2 -- it basically hit the max of 5.35A.
I'm thinking/hoping the 4.2A on the XP-G2 is not all the light - something goin on with the LED, but can't be sure at this point.
You could argue for the excessive size/weight, but it's a big reflector budget light with 4 26650 cells -- so what do you expect?
Seems to me it’s just a bit larger than my TrustFire TR-S700, which is a 3x26650 hand-held, so size-wise, not a problem for me.
This must be BLF, on the one hand it’s stated that it does 547Kcd, on the other hand “… if I can’t get it to perform…”.
That’s funny!
648Kcd is a mile. Just sayin.
Hey Tom, what are the reflector dimensions? (I’m hoping you say 95mm diameter, 65mm tall)
I am hoping that we can get a real good group buy price on these. I think this is a good candidate for those old monster lanterns. A DD driver with a couple modes would make this thing spot on. High for searching and low for "just need a light". Maybe even L-M-H. Best of all...run time.
I have a couple old Milwaukee 28V battery packs that look like they have the paper 26700's. I think they would be perfect for this thing. It is big and heavy but when you need super long run times why not....at least one ;)
I could be up to 10% low on my throw #'s because of 5m measured (happened with a modded TN31), and of course an AR lens difference on top of that could be another 10%, then you are in 1 mile territory. I might do little more testing to see if I can boost the 4.20A, then either dedome the U41C or try a dedomed V6 1A. I really need to test dedomed XP-G2's - maybe this one, try in another DD light, or work on my XP-G2 hot dedoming - I got a ton of obsolete ones for sure, but this time measure before/after Vf at set amps. I think my bench PS is good for that, not sure how accurate, but relative measurements should be fine.
The hot spot sure looks intense...
Post #108. CWK did a pretty good job reporting the dims early on - don't think I confirmed them all, but some dims I took are only fractions off from mine, so I trust his numbers.
I knew I saw it somewhere, but couldn’t find it when I wanted it; thanks. Those dimensions I listed are for the Lum 5-90 reflector. I have one, but haven’t found a light that fits it yet. Maybe with a little trimming…
What kind of kcd do you think we could get from an XHP-50 at max output in a 90mm reflector?
how about using 4,35v 18650 cells ? That should deliver more amps to the emitter
4.35v cells are not as low resistance as the better high performance 4.20v cells. The EFEST 4200 mAh 40A/60A cells I'm using seem like the best cells on the planet right now, least what I'm seeing. I think they are doing little better than 30Q's and HE2's.
Relating to batteries:
The threads on the battery tube are starting to get beat up. It's not easy to start the battery tube threading - you fight the bumps and the threads take the force of it, since they are very pointy (not square) and it's sooo wide, it's really hard to get the threading started now. I'm afraid this is only gonna get worse. I'll have to take a closer look at the thread damage later.
The lack of squared off threads on such a big light might with such resistance of 4 cells could be the worse design issue.
Is there a possibility of contacting the manufacturer to improve the threads on the tube/retaining ring, and maybe the machining of the shelf? Even if it adds $5-15 cost per light it would be absolutely worth it imo.
I thought of them not because of their resistance, but because xp-g2 leds have higher Vf and therefore should deliver more amps to the xp-g2.
It doesn't work that way though - you only see 4.35v with no load. They drop like a rock under high draw. I know this from the past, but more recently re-tested - same results, worse than say an HE2 or 30Q, etc.
Also, it won’t take much more to fry the XP-G2… it can usually go up to 5A but isn’t good for much more than that. With some power-on fluctuations and such, gotta be a bit careful not to be too close to the ceiling on those.
Interesting work there Tom, thanks for taking the time and going to all the effort.
with regards to the contact “bumps”, is there a way to mod the whole driver board into something like this from Courui d01? ? No bumps, just flat PCB cut to this or similar shape
that should relieve most of the pressure on threads and even lower the resistance by increasing contact area
If you can get the bumps off somehow (sand them down?) you can just use a washer in their place.
for instance a single large piece of a thin copper sheet like this 99.9 Pure Copper CU Metal Sheet Plate 100x100x1mm for Handicraft Aerospace for sale online | eBay or this
http://www.ebay.com/itm/1pcs-0-5-x-100-x-100MM-99-9-Pure-Copper-Cu-Metal-Sheet-Foil-/291644627765?hash=item43e75fdb35:g:AN8AAOSwEetWAkC7
Possible I suppose. I looked closer at the thread - don't think there's damage but the anodizing seems to be coming off on the first thread - think that's why it looked worse than it is. Still, it's a challenge every time to get the threading started.
Decided I'm gonna go ahead and piggyback in a 20 mm driver, and go with the U4 1C I was using, but de-domed. I added a couple more trace jumpers, and added 2 screws to secure down the LED shelf. Since the darn thing is so loose, it's a PIA to assemble the light. I'll just add thin layer of thermal grease on the overlap shelf, then the 2 screws will hold it tight all together.
Ohh - the flat edge in the body that the LED shelf rests on is exactly 5.0 mm wide 
.
Been side tracked a bit on a L2 mod, and driver issues.
I ended up using the dedomed U4 1C in the L2, after finding a broken bond wire in a under-performing dedomed V6 1A for the L2, so I dedomed a U4 1A for the BOSS1 - took a few hours in gas but came out look'n perfect. First tested on one EFEST 26650 cell, and got almost 5A, then tried with all 4 cells before assembling the reflector/head, and all I got was a quick flash, then nothing. Looks like I popped the LED - it's dead now. I can't make out a break in the bond wires, but can't be sure - I really need a microscope, hard to tell with the 20X-30X cheap magnifiers I got.
I always though the high Vf of these new XM-L2's would protect them from going over the point of popping, but using 4 high power cells in parallel, combined with no driver was probably too much, or, the dedomed XM-L2's can't take as much amps - not sure.
I'm out of FET's right now to build a driver, and low on parts - put in orders with MtnE and Mouser. So, guess my next mod will be to add a driver and try another possible sacrificial dedomed LED.
The tube threads aren't as bad as I thought now - they are holding up, and the driver retaining ring is holding up so far, but I'm being really careful with it. I got spoiled on the new Convoy L2 threads, but the L2 also has a very thin driver retaining ring, but out of brass, not aluminum.