Wow , i just noticed this is a 5 yo flashlight review ! Very interesting !
Yes , you can try adding another resistor over the 2 resistors you mentioned . These are probably limiting the current . you can try adding a resistor about 150mohms , or lower value . Edit : I thought one resistor was 100mOhms but it’s 10mOhms . Hmm… I don’t know if these are the sense resistors .
I would do a full mod on such a gem , 4 brand new leds on copper mcpcbs and a fet driver 
That was my thought too. Which emitters though? No sense making it a thrower, right? So aim for a big flood of light?
I’d like to change/short sense resistors on the stock XM-L’s to start; so can someone confirm what to do on this driver? Or I could just direct-drive it :smiling_imp:
-Garry
Lot’s of choices …
For a good tint (neutral white for me) and output combo , i would go for xpl v6 3d probably , which have very good output … Nichia 219C are another option of course .
For maximum output : xp-l2 or sst-40
These , and a fet driver would be awesome .
Is the driver 17mm ? If yes , you could use the cheap BLF A6 driver from Banggood …
20mm driver (had to read back in my own review). Weren’t there 17mm to 20mm brass adapter rings available back in the day? Think I have something like that. 219C’s sound more along the lines of my budget, but what kind of output difference would you expect between 4x 219C’s and 4x XP-L / XP-L2’s? Remember, this is a single 26650 light, so it may be severely limited trying to push 4 XP-L’s, whereas it should push the 219C’s much easier (correct?).
-Garry
Yes ther are still adapters like that . You can get a 20mm driver from MTN but of course it will cost more .
I haven’t build xpl quad but that’s what i think . xpl will be brighter for sure . For example : Using values from the datasheets 4* xp-l v6 at 9,6 amps will have 3700 lumens output while 219C (D240 bin) only 2700 lumens . 121 lumens/watt vs 81 lumens/watt .
A good 26650 cell will handle both 219C and xpl fine . I know for sure there are 20-30 amps cells .
I would put in 4 dedomed XPL or XPL HIs. It’s just a matter of what you want the light to be. Domed XPLs will give the same size beam as stock, just brighter. The XPL HIs will give a beam about 2/3 the width, but nearly 2x more intense than the XPLs.