Thanks for letting everyone know. 
I wasn’t sure whether to wait for the problem’s to be sorted out with the Cometa and then buy one or to just buy the Jax Z1 elsewhere, I know now. 
Sharpie reports at that the Cu and Al X5 and X6 light parts Lego together fine, correcting what I thought I’d read somewhere:
This — sorry to say it’s sold out — is a body-and-tailcap that was being closed out recently.
Turns out it fits the head and tailcap threads of the X5, though the threads aren’t long enough and it needs an extra retaining ring or other filler to light up.
http://www.kaidomain.com/Product/Details.S022509
http://manager.kaidomain.com/UploadFiles/635140376727690000_med.jpg
“Optiled” is the name on the tube.
Astrolux S41 and bare BLF A6 lego perfectly fine with each other. I can interchange heads, long or short tubes and switches as I want. Both lights work in any combination!
I was recently made aware by a fellow member that there is actually one component of the Jaxman Z1 that will lego with the Cometa. As I received a Jaxman Z1 a couple of days ago, I can now verify the information is 100% true. The component legos perfectly… :+1:
The component would be ………………………………………. the lens cap. :person_facepalming:
The lens swaps too. I’m actually running the Z1 lens on my Cometa, because I have the old XP-G2 de-domed pulling 5.65 amps and it boosted the LUX up a bit. They fit each other better, no moving the lens around to get it on center. Weird!
:+1: Thanks, I was unaware of that. Good info…….
Cross-reference for discussion elsewhere (Reddit’s flashlight forum)
Reddit summaries are sometimes useful when people haven’t been ‘through the wars’ as things developed and are wondering “what legos with what”
Brief excerpt follows; more at the original page of course
https://www.reddit.com/r/flashlight/comments/4jfc9f/eagle_eye_hosts/
EE hosts are at: http://www.aliexpress.com/store/1735126/search?origin=y&SearchText=host
And I”m wondering if there are triple spacers and optics made or that happen to fit them.
xref for discussion at BLF: Eagle Eye X6 black flashlight host on AliExpress
Astrolux SC/Ultrafire C3 SS (1st version, 93mm).
LOL, and so it does, not very useful perhaps, but a great find! 
Skilhunt DS16 legos with Manker E14 / Astrolight S41. The threads where the head and body tube match and are interchangeable.
Note however that the skilhunt is an e-switch light and lacks a tailcap switch, so the usefulness of legoing with the astrolight except for an advanced modder, is pretty much nil.
On the other hand, if you have the astrolight you can get 18650 support using the Manker 18650 tube. Note however that the Manker’s o-ring won’t be covered.
Ordered both the SS and AL versions of the Ultrafire C3 from DX to see if they both fit the x5.
Cross-reference for mention of various Convoy lights:
Ordered done flashlights from DX on 7/11, the shipment was broken up into 3 separate packages and the first of them arrive on Friday 7/22 a new record for them. Jolly good show! In this package were a couple cheap AA lights. A Sipik SK68 and an Ultrafire C3. I was particularly interested in the C3 as I had heard a version of it would Lego with my copper X5 and this I can happily confirm. 
Also of interest is that those cheap no name cree AA lights from eBay also Lego with the SK 68, the tail caps are interchangeable and the tubes thread together so you can easily make an xhp50 zoomie. 
Yup fits… need to add a wire ring behind the driver retainer for it to make contact.
!
!
That’s the SS version, right? I’ve one of those in the order as well. Is that a recent purchase? Mine works without a wire.
It is the SS, bought about a year ago. Fits well and looks pretty good. It is the 93mm version.
I would not fire it up with the stock C3 switch, that light will draw way to much current for that switch!
My SS C3 from DX came yesterday and it does indeed fit the copper X5 very well and works just fine. 
Although the longer threading of the X5 tube does not go all the way into the head or tail of the C3. 