We have a ROT66 killer over here. Without lightened switch, aux led, charging ports and other gimmicks.
3*18650 format is comfortable even for holding the light for long.
I hope you make a 21700 D4 or D4S once.
CCT mixing will result in a better tint, but figuring out how to do it in this light gives me a headache 
Does it have D4 UI V2, V3 or Anduril?
That’s a rather odd place for a lanyard hole since the hand will be placed over it. And it looks sharp.
@Hank, the 3000K and 4000K SST-20’s you have in stock are binned above the BBL thus the tint of them isn’t super appealing. The 3500K version BlueSwordM sells is binned below the BBL (GA3 tint bin). Can you make a D18 with them after sending these leds to you? Or maybe you are willing so source them. Or selling a D18 without leds and with an adequate lower price.