I used an overkill driver from I-O that would work. It’s a buck-boost, which works fine for driving the MT-G2 from 2 18650, so an 8S would work. I think there must be better drivers for the task.
I think a 4S2P config is better, which limits you to XM-L/L2 or MT-G2 with a boost driver.
This might work OK for driving an MT-G2 from 8S NiMH.
More photos in the OP.
I probably will wait till I can buy one of the Taskled drivers. The fact that they are thin makes a big difference in the limited space I have. I am concerned about room with the fatty drivers that take several mm of height space. When I can, I will buy one of George's drivers and finish the build.
That is so sweet lookin. Someone linked to another forum for me to look at. I thought you may be interested as well.
Reserved
More photos in the OP and a question about a component. Photos in the OP show the component in question.
Those are diodes, I assume to prevent a reversed battery condition from breaking things. I would not have expected it in the tailcap though…
If you replace them with bridges you will lose that function, but you may also not care depending on the driver you use.
I was wondering if that is what they are, but it did seem strange to be in the contact plate. I may just leave them if that’s the case. Since I am going to do 8 in series, I have to put in a 3rd guide pin, so that the tail cap can only go on one way, as it can be on or 180 on now. Can’t have that with 8 in series.
I think it makes sense there, as they are somewhat sizeable components due to the current and possible heat dissipation needs, as well as to provide a battery bridge. Just checked my EA4W and according to my DMM, and it’s just a straight bridge. Guess they weren’t as concerned about reverse polarity with the little guys.
KuoH
On the EA4 the circuit can be seen it's a straight thick trace, so I guess DMM check is not needed.
You are setting the bar so high OL I’m going to have to take up pole vault. Tell me you punched out the little copper round tabs and not cut them out by hand and file them to shape on the battery board?
I modded a 16mm XM-L star to use for a pcb for the smd switch, photos in the OP.
@MRsDNF - I bought the pre-cut copper rounds 3/8" diameter.
I like the use of the pcb for the smd switch. Very clever. I wonder if the stock board could be modded(sense resistor change) for more output or if the components are already maxed out.
There is a sense resistor there, just waiting to be tested. 
Sorry if this is O/T but all the smart folks likely to have done this before are already in here... anybody know of a source for parts to build a drop-out battery carrier? Specifically the female threaded rod to tie the two plates together. I can make the contact boards easy enough, but for the rods I don't know where to look or really even what I need to go look for.
Check Digikey or Newark. We used to get shorter ones from there. They are called standoffs. You can get aluminum, aluminium, brass, or nylon.
I got the driver. It came from taskled. It's the b3flex. I could not fit the h6flex driver in (too big around), so I had to go with the b3flex.
I am waiting on the led and when it comes in, I know I will just slap it all together without photos, so I put up what photos I could now, in the OP.
I just didn't want anyone thinking I had forgotten this thread. It's still WIP.
" ... slap it all together ..." he says .
sure .
Reverse polarity protection diodes. I guess not altogether a bad idea, considering they seem to have designed everything on this light to be as complex as possible for no good reason! lol
oh yes, with your track record i would assume you put it back to stock to bask in its crappy engineering 