Congrats on selling the light, it is a great light!
But I do not really understand the current you get with a lineair driver (with no boosting). Either your led is way out of spec, or it is a different one than the LZ1-00UV00 that I used for my small zoomie mod, that claims the following (from the spec-sheet):
What I read here is that with a fully loaded 18650 with no voltage losses underway and no sag at all (so 4.2V) you can still expect only 800mA, in a normal flashlight situation less than 600mA. What do I miss?