Congrats to you 1k Posts -> you know what that means 
yes - 4 x XHP35 will work
but they willl be very dim!
i use mine as a host for a 1x XHP35 + lens project
I imagine the LEDs require more volt, right?
Can this fixed by replacing components in the driver?
The latest Zebralight SC600 mk3 utilises XHP35 emitter, but their buck-boost drivers are most probably not budget-friendly
the stock driver can handle the voltage, but not the Amps
6 amps for 4 xhps in parallel would be enough. I see your measurements and I believe the power is enough.
Edit: it is 2.5amps, not 6.
Adding some sense resistors will help?
if you want 2,5A at every emitter you will need 10Amp from the driver
2.5 amps total is plenty. Parallel 0.625 amps each is still 1240 Lumens each with highest bin XHP35 HD. You amps junkies are going to have to rethink XHP35’s 1.5 amps probably absolute max. Cree announced how it was going to incorporate SC5 technology into the XP-L and XP-G2’s to boost output last month. That technology is already in the XHP series. Look at 4 cell series and 4 LED series light set ups. Now think 4 cell series 4 XHP LED parallel and the SC5 tech is already built in to boost lumen/watt efficiency. Same wattage and all the numbers put XHP35’s higher than XP-L’s. Add to that and quad XP-L’s and XM-L2’s need a slightly higher forward voltage over the XHP35. I specifically picked the XHP35 over the XHP50’s and 70’s because you’re not going to have to alter the reflectors.
Wow! 
I would never be brave enough to tear open a TM! You must have gotten a good price and be very confident that you know what you are doing! It is really neat to see the pros and cons of the nitecore builds!
Samsung just released a great new battery for this or any light
Samsung 35E 18650 3500mAh 10A
https://www.imrbatteries.com/samsung-35e-18650-3500mah-10a-flat-top-battery/?mc_cid=b7187dd655&mc_eid=23d0a20bfa
Just a matter of time b4 they have it in button top if not already
It’s not really new, here are some charts
Nice review, very much enjoy the intense testing and charts.
I got my second TM16 (gave away the first in my 10,000 post giveaway) just the other day and got inside but it was quite the chore! Have some components on order to upgrade output and beam tint, will be getting copper DTP under the emitters as well.
Thank you for taking the time, and from what I see here, it obviously took some serious time! 