Have you a caliper which can measure millimetres?
M size is the OD of the thread.
What is the max temp that should ever be reached?
I’m testing mine out, and it became too hot to touch without ramping down.
After donning gloves to turn it off, it self-reported a temp of 84C.
What I did:
inserted 30Qs charged to 4.15V.
ramped all the way up
left it upright on tail for a few minutes (at some point it ramped down)
turned it off
checked voltage and temp (I think it was 4.0V and 51C)
turned it back on to turbo
At this point, it did not ramp down.
After the light had been off for a few minutes, I opened it, and the batteries were on the verge of being too hot to touch, so I’m guessing about 60C.
I apear to have version 1 of the firmware from off: (3 fast clicks, then two fast clicks, then two fast clicks) results in one flash, long delay, one flash, etc)
They are mostly used in Laptops and elektronics.
The head is under 1mm (https://de.aliexpress.com/store/product/500pcs-m2-5-9-cm2-5-CM-Thin-flat-head-philips-machine-screw-computer-screw-steel/2959029_32802558165.html?spm=a2g0x.12010612.0.0.38f4b823WZulwr).
You can get them for Philips screwdriver or for Hex key. And also with different head diameter. The link from Ali is only a example.
Google Thin Head screws and search for pictures. A lot of different ones to get.
Narsil M v1.0 is the newest version. thats OK
NarsilM / Narsil Timeline
2016-07 Narsil v1.12
2016-09 Narsil v1.1 (because only two digits blink out)
2016-09 Narsil v1.2
2016-10 fork to Narsil Triple
2017-04 Narsil v1.3
2017-05 NarsilM v1.0 (Narsil Multi, combines Narsil 1.3 and Narsil Triple)
I measured 2.91 mm on the threads, so think they are 3M. The protos were 2.5M.
From left to right: proto round 2, proto round 3, production:
The driver PCB holes are much smaller than with round 2, so you basically are threading the screw thru the driver PCB. No bevels in the drill holes
It is a bit disapointing that they have used so cheap and not really fitting screws if a few thousand Flat head screws (pretreated with some kinde of loctite) would have cost maybe 20$. I think they are making more money at the 40$ than we thought. You can get a code that brings the price below 50$ if i am right and on Ali it is even cheaper. Do not get me wrong i am absolut happy to get the light for 40 + extra for shipping but i would be really interested in knowing what the real production price for 1 unit is.
But that is something we will never get out of them.
I can see me now, trying to mount the tiny screw on the lathe and undercutting the bevel to make a flat panhead style. Like giving a lobotomy to a flea. 
hard to believe the decision on the screws was based on profit margin
half a cent x 4 x 2000, it adds up. 
It was a challenge to get those screws out. Even after loosening them, they were tightly threaded thru the PCB. They ain't going anywhere, and they got clearance. We knew they eliminated the plastics shroud rings, but they didn't say anything about changing the screws.
My first thought, as well, but I would probably do it on the wood lathe with free hand tool.
Indeed, I find that unlikely. And if we’re stuck at arguing about screws which have yet to show any sign of failure, I think we can say the project is a success.
Just curious… what were you you thinking they were making at $40??
I do not know what they are making on each light. But it seems that they are making enough profit if they are selling them so close to the GB price.
And i do not know if the srews are a price decision but most of the time very soft extremly cheap countersunk screws are costing at most 1/2 of the Flathead ones. Like i said it seems that the other ones are working and i am not saying that everyone has to change them. But it itches me like hell. It does not look nice or right. And with the Flathead screw there is no chance at all of shorting out.
There is a Beamshoot comparison in the MF01 thread
Astrolux MF01 (18x 219c)- ~10000+lm
BLF Q8- 5600lm
m43 Meteor 219c D320- 7400lm
Olight X7 NW- 8900lm
MK34vn (Manker gemoddet xpl-hi 4000k)- 7400lm
Oh… I agree with you. And like you said above… it would be interesting to know production price per unit. I’m betting it is a lot less than most would think.
Which is just fine…… they did not do this for fun & giggles. 
I be just happy to get mine . Lol
What is the best diffuser to use this light as a lantern? Looking something for camping etc.
Disposable plastic tumbler that’s translucent (as opposed to transparent/clear).
On costs, I've heard this before. At the company I work with, if the manufacturing costs are more than 1/3 the selling price, we are not making money. There's lots of costs to consider. ThorFire said they basically aren't making money at this price, and I believe them. I dunno about that Ali store, if anyone who ordered Q8's will ever get one from there, but I don't think we'll see the under $50 price for very long. Probably the quantity has helped. Just the cost of 4 XPL V6 3D's and a 2 mm copper DTP large MCPCB, for us, would be about $27, add shipping, packaging, warranty support, service, PP and credit card fees, plus there's NRE costs, which I can't see as less than $50K on this project, even in China, is $25 per piece at qty 2,000.