Well to me I will always buy the version with highest output power available (i.e. 2.8A in your case) because whenever I need longer runtime I can always change into lower mode. That’s what the multiple modes selections are for, right? 
For this size light or larger with XM-L, always get the highest powered driver option available. If its too bright or becomes too hot, put it in medium mode. Outdoors, there will be a considerable difference in performance & range between 2.1A vs 2.8A.
Thanks for the info JohnnyC, I appreciate the quick reply 
Dose anyone know if the micro controller can be reprogrammed by an in service programmer such as discussed elsewhere on BLF (like with audrino or the like)?
Yup, it sure can :) Check out http://flashlightwiki.com/AVR_Drivers. The driver that comes in it is a NANJG 105c, just with a different firmware.
Glad to see you want to go the DIY route - it's a lot more fun!
Good lord you’re fast, and useful too thanks for the reply and the link
All true but you forgot one important thing:
flashlight is for his parents most likely older people and in my experience older people don’t like complications with modes and what not, in their time flashlights had only ON and OFF, very easy to use, now you have to explain what is power on/off cycle and what is mild tap for mode changing, then there is a memory so they have to be relatively fast when switching modes otherwise flashlight will memorise curent mode and so on.
It is easy for us flashlightoholics but they just want something that will produce light and will be reliable.
Another issue are batteries, older people know about AA and AAA (TV remote as they call them) batteries, some also known for C and D batteries but most of them didn’t even heard about lithium-ion or 18650, 14500 etc. Try to explain to them that they need new charger for 18650 batteries and that this batteries need extra care and they will immediately say: “no thanks, I will use my old (incandescent-crappy-barely shines 2 meters-light) flashlight”…
With that scenario it is best to go slowly, let them use the light until they see how good it is and just replace battery from time to time, you can teach them about li-ion’s later.
Because of all this I think that 2100mA version is better solution, older people don’t need ~900 lumens and 200 meters of throw but longer runtime will sure make a difference, they wouldn’t have to worry about that and priest77 would not have to exchange battery so often.
Also, I would reprogram the driver to only one mode, very easy to use, just what older people like to hear about new tech
@Sirius9
You’re right, I’ve ordered a 2100mA version and I will do the charging for them…
Later if I like this C8, I’ll buy a 2800mA version for me. Now I can’t decide what is better choise: C8 or UF-T20 or other zoomie, for me… do I need a zoomie?
Thanks to all for your help!
I agree! 
I once gave an UltraFire C8 - complete with 2 Sanyo UR18650Fs and a charger - to my dad because his old incan flashlight ‘consumes’ a lot of alkaline batteries and it can hardly illuminate beyond 5 meters. I later found out that he just placed the C8 in a shelf and never used it despite the fact that it is much brighter than his incan and that he can save a lot by using the rechargeable lithium ions I gave him instead of stacking D-Size alkalines.
When I asked him why, he simply told me that he ‘HATED’ the blinking (strobe & SOS), the need to go through all the modes to go to the output he desired, and the ‘blinding’ beam of the C8. I ordered the generic 1-mode 4 AMC7135 driver from FastTech and installed it in his C8 it it suited him perfectly.
He asked me to buy him a holster and his C8 now stays with him wherever he goes - even when he sleeps. :bigsmile:
Yup, exactly. Most of the ‘older folks’ with the old school mindset just want something ‘basic’ (‘long’ battery life, probably one medium low (what we call 30% or so), mode, click for on - click again for off. Nothing at all about batteries to ’deal with (when it runs out, put on charger, when it turns green take it off charger; never worry about voltage levels, overdischarge/charge or anything).
Most of us on the other hand, do not mind any of these things being different and simply want the absolute most possible output from the smallest possible die for that output and a very very large plano-convex aspheric so we can light up stuff over a mile away enough to see from that full mile or even more if possible (well a hell of a lot more than even that actually, even if not possible it’s what we want
But you nailed it (and a few posters before as well), the idea is a satisfied recipient.
Since my dad uses his C8 that I gave to him seldomly, I do not even let him to charge the battery, I charge for him. 
Mine arrived today. Compared to other C8’s I have, including KD, I like the less glossy anodizing and the improved tailcap switch. And I really like the reflector centering device mounted permanently around the LED - no out of round patterns. I’m sure if I ever mod this light, I will also appreciate the 2-piece pill. Compared to most other C8’s and C12’s I have, it has visibly comparable output, but the tailcap current measurements baffle me. All the others I have run 2.9 to 3.1 Amps (except a brighter one that runs 3.9A!), but this “2.8A” regulator only runs 2.47A, regardless of battery - including an XTAR 18700. Further testing is ahead.
my first XM-L light had that problem, one of the 7135 chips was not working, the pcb was cracked because they installed it with so much force it cracked (and had to be destroyed to be removed)
I’m considering buying this torch, wondering about heating factor, how good is it ?
I maybe asking dumb question but I have to ask. It operates on 8* AMC7135, so I suppose it using constant current not so efficient ? (which oppose to buck driver which more efficient at higher battery voltage eg.: >3.8V) Is the efficiency approximately same in 3 different mode ?
Since LED using voltage lesser than 3.3V most of the time ?
It will be hot but too hot too touch because of the C8’s big head. I think many guys here have modded their C8 to a higher amperage than that. This is a linear driver. The test on this driver is Led Driver test July 2013 Check out “3 to 4.5 volt 2800mAh driver (FastTech 1122302 Nanjg 105c)” section.
Where are Convoy XM-L2 versions available?
Got one on table but cannot remember where I ordered it
edit: found it! Aliexpress.
note, it is not the same model, dimensions are a bit different, pill is significantly different and you can use batteries up to 67mm tops…
Hi, after reading this review and that of the M1, it is difficult to choose one of them. What would be the main differences and which one (host and configuration) would you recommend for a helmet lamp to an inline skater? - you want to have some field of view and detail in addition to the actual reach of the light (which is a plus anyway, but not everything). I am worried about the XM-L-U2 1B being too white and masking texture/detail but it seems to provide the maximum intensity. Thanks
UPDATE: just found this other thread addressing just this: Should I get a Convoy M1, M2 or C8? So Confused!
In any case, any further thoughts or advice on the intensity/vs tint?
For me, Neutral White is good balance between tint and intensity. NW 3C is good for me (I got in EE X6 SE)
This one will have a smaller hotspot and light things up further away (think several city blocks) and the M1 will have a larger hotspot and is better for closer things.
Cool white (higher K numbers) will be very white and even slightly blue, warm white is yellow like regular old style light bulbs (2700-3000K) and neutral white is in between and likely what you want
Either of these lights will easily blind other people who look in your direction so i’m not sure you should use either of them
Thanks for the input guys. I have decided to go for an s2 with a xm-L2 T6-4C instead, because I think that it is more important for this application to have a more neutral tint and better flood to perceive better the obstacles in the closer range. Just hope that the throw is enough to perceive them soon enough. Didn’t find any m1 with the XM-L2 version and the XM-L-U2 seems powerful but very cold light. For the price that these babies have it won’t be a big mistake anyway.
As for Bort’s observation, this is mainly for use in reserved bike lanes and the lightas are mounted in the helmet pointing downward, we somehow control the level of the beam by looking further op or down when we cross someone, which is not too often. Bike lights blind us too, no big deal. Would you have a better suggestion?