THANKS GARY, JUST THE INFO I NEEDED
My A123 battery is tight and got stuck.Found it easy to remove since body is splitable behind the head.
Lennart
I’ve got the ultrafire clone of the POPPAS 878:
It must have a different driver as I’ve had the following tailcap readings, off of a King King unprotected 26650:
At 4.2V 2.69A
At 3.9V 2.25A
At 3.6V 1.6A
Current reduces as the voltage lowers. It’s very bright with a fully charged battery. I’m pretty happy with it, and the zoomy head seems pretty stiff and hasn’t yet automatically zoomed on me when nightriding on the mountain bike. It also makes a great emergency replacement room light if you blow a bulb.
I took my poppas apart and did have closer look what it have been eating. Unscrewing the pill was kind of hard… It was so tight that i thought there is some clue in threads, so i even warmed the head little bit ( there was no clue ). After a little struggle ( and many scratches later 
) I did get that pill unscrewed. Leather clow and long head pincers was the key.
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There is reason for this. It does not only feel like that, it really scrathes metal against metal. When you unscrew pill you can take head of and there is place for o-ring in body. Apparently torch builders thought that metal ring is better than rubber o-ring (???). So I recommend to change that. After changing sliding head is sooo smooth ;). Here’s picture with stock metal one on table and blue o-ring but as replacement on body. You can even but thicker o-ring if you want adjusting to be more stiffer. Sure that o-ring can’t take as much stress as metal ring and maybe some harder plastic ring would be best option. But I think that quality and tight o-ring with grease on it will last as long as light it self.
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Garry already told about one missing o-ring, but here’s picture of that. I have put blue ring on there so you can see that place better.
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Tail-cap reading from my light on high is 2.74A with TF flame 26650. It’s also steady now ( pushing battery does not increase amperes ) ’cause I welded cord in drivers spring.
Interesting. So does the head remain stiff (stay in place) now even with the o-ring? That's what I want - the head not sliding by accident.
-Garry
When I do few snappy hammer motions the head did slide about 1-2mm. Even it is much better now it still could be little stiffer to avoid all accidents.
I try to remember today to pick thicker o-ring from work and try with that. I’m sure then it will be pretty stiff.
I changed o-ring to little thicker (about 19x2mm). 19mm o-ring needed some stretchning ’cause that heads diameter is 30mm (bigger diameter rings that I had was too thick). But it snaped nicely in its place.
Now that head is stiff. It won’t move by accident, I’m pretty sure about that. I “hammered” with flashlight few times hard and that head remained same place where I left it.
This is how it should have worked in first place. 
Ordered/shipped on 11/12, any day now hopefully. Was looking for a light to use a single 26650, and the flood on this one sounds nice. Looks like it need some TLC - when I get it, I'll be studying this thread carefully - thanks for all the info!!
I would be interested in upgrading to a KD V2 3.04A driver, maybe add 1-2 380's to it (3.4A-3.8A). It looks like an aluminum pill however - wonder if there's a brass ring to solder to. If it's solid aluminum, it's a pain but I'm experienced with the cheap stuff!
Just got this light, bad news with this light - no flat surface/heat sink for the LED star mount. LED is loose, floating, and hangs on the edges, same as a driver does on the opposite end of the pill. I've seen this before in a cheap zoomie. Does anyone have any ideas? I could use good thermal grease or thermal epoxy on the edges, or press fit something inside the pill, but to get it aligned perfectly to the back of the star may be a nightmare. There is plenty of depth in the pill to work with.
I ordered the Poppas S7, that's what the links for the 878 take you to now - looks like Manafont changed the model name listed but appears to be the identical light, accept maybe for the hole at the top of the pill 
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Solved it - I got several brass pills from FancyFlashLights and sanded one down to build a press-fit insert, flush fit behind the star - worked well, also added copper/solder into it for additional heat sinking. I'll post pics. I'm using a 2nd brass pill to convert the 20mm driver mount to 17. This light has a big aluminum pill, massive now will the copper, solder, 2 brass pills, so I'm putting in a KD V2 running 3.8 amps (10*7135).
Update: I got it working at 3.4A, still will update it to 3.8A. At 3.4A, it's nice, real nice - my most powerful zoomie but all my other zoomies are cheap and small. With a 26650 and all the mass I added, it's heavy, feels solid. Really like the width of it in full flood (truly lights up a full room, more than a HD2010 or modded C8) and in throw, the square image is smaller than my other T6/U2 FTT's and it throws pretty well - not as much as a HD2010, Jacob, or maybe even my modded C8 at 3.8A/U3. It takes quite a while to get warm/hot which is what I expected with all thah mass - used Arctic Silver grease, not epoxy, on the star because the reflector screws down onto the star to keep it firmly in place.
More Updates (12/09/12 eve):
Got it working at 3.8A now - really like this light now! Using a King Kong, lot of mass, tailstands, just need to add a nice GITD lanyard and a holster.
Work Bench:
The hole under where the star was, and the sanded down pill to use as the star backing:
Close up of the sanded down pill:
Sanded down pill with the original pill, before sanding:
After mounted:
Showing the heat sink additions (cut copper wire, held together with solder), and the next pill sanded down for mounting the 20mm driver:
Up close view of sanded pill before press-fitting into place:
Final assembly (no pic) has the original pill with the star backing pill with heat sink filler, and the other brass pill for mounting the 17mm driver in. This thing is now heavy!
Thanks Tom for the photos! Never realized this one had a hollow pill. I've run mine on a King Kong unprotected at 4.0A+ for a few minutes at a time too!.
BTW - is that an older Kenwood receiver I spot down there under your workbench?
-Garry
Garry - could be the original 878 was ok, but the Poppas S7 replacement has it missing. If you go to the link for the 878, you get the S7 light with the earlier 878 reviews posted, including yours! Think they cheapened out in the redesign. Thought I saw a pic on BLF of the 878 pill showing it had the full backing for the star.
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Update: hhhmm, not a Kenwood, but kind of got stuck there - nowhere else to go with it for now.
Garry - did you verify you have the 878? Was wondering if the S7 model cheaped out. here's the 878 pill posted back in April and it definitely shows a solid backing behind the star, but no thermal grease: https://budgetlightforum.com/t/-/7687. You posted there as well.
Ok, I haven't opened mine up (nor do I remember investigating this), but I am pretty sure your hunch is correct that they cheapened things up and at least had the decency to change the model number while doing so. Mine is definitely the older 878 model. Could you (or have you already) post a review over at Manafont with your findings on the hollow pill?
So, if you don't mind me asking, what is it? (I'm just curious.)
-Garry
Really like this light now: U2, 3.8A KD V2 driver, and all that heat-sinking - takes a few mins at least before warming up. Yes - I should definitely post a review up there, maybe this eve, at work now.
Hhmmm, trying to recall about the receiver, forgot to check last night, it's a name brand - good for it's time. Ran out of space in the living room for it when upgraded to a big flat screen. @work now, will check tonight and let u know - it's bugging me now 
. Onkyo or Yamaha, thats' it! I'll check tonight.
I see now the older Kenwood's I was thinking of don't look like that at all on the rear. Looking again I'm thinking your receiver isn't as old I first thought. I've kind of had a thing for older receivers. I'm still using my 1990 Pioneer VSX-4400 bought when I was 14. (I have yet to upgrade to a modern home theater receiver.) I also have a big ol' tank Kenwood (not sure of the model number) which is all analog from the mid '70's that just looks cool with all it's knobs and dials.
-Garry
Finally posted the review on this new S7 - 2 stars, "Dont Buy" because of the top missing from the pill. Also mentioned earlier posted reviews were on a different model.
Looks like an Onkyo to me, late 90’s to early 2000’s maybe?
Let us know.
Thanks,
Keith (sold Hi-Fi for 15 years)
Oh - forgot to post this -> it's a Yamaha, model HTR-5560, 290 watts. Time frame is about right, not sure, couldn't find a date on it.
I have a Fasttech SKU, 1864903, 
which they call a TrustFire 878, though there is no brand or model information on the light. Since Fasttech tends to be reliable, I suppose it is really made by TrustFire but that TrustFire either had a fit of modesty or a broken engraving machine and left their name off. I intend to read this review and report any interesting differences. I found it going through Fasttech’s web site.
The first difference is that it comes with a 4xAAA carrier that also fits in other 26650 lights. So it would have good output as a gift to a non lightoholic. And mine did not come with a 18650 spacer.
It will be useful to me at least as a hanging lamp, because of the long run time and the better light distribution of a zoomy with a diffuser, compared to a reflector light with a diffuser.
2 The lens is captivated in the bezel ring by crimping, as it is usually done, not by glue, but that might be a mistake in the OP.