Damn glad to see the J12 get the 2100 treatment. Fantastic work and now you can trust me when I give you lux readings. LOL I honestly though the J12 might edge out the DRY, but that's OK. Its a testament to how well put-together the DRY is.
I get the almost the same currents with the KKs as you are with 18650s. 3A still isn't that much of a challenge for good 18650s. Keep in mind that since it is wired in parallel, the fewer the cells, the closer the battery voltage is to the Vf of the LEDs and that results in the driver working more efficiently. That explains the better performance on 2 cells and a good reason to have four cells (2 for backup) and throw out the extender. :) All of my lux testing has been done with 3 cells, so I think I may try 2 x A123 cells. :)
Thanks for measuring the PWM too. I knew it was low. I'm generally not bothered by it, but I think I've found my threshold.