Saw Q's earlier on performance of a hot rod 14500 light - the copper or alum K6 in this case. I fully modded a ThorFire TG06 with basically the same wight FET+1 driver - post #52 here: https://budgetlightforum.com/t/-/33146. I got more amps/output with the WindyFire cell at 4.02A tail, as opposed to the EFEST IMR V2 700 mAh cell, or SANYO 840 mAh cell - both about 3.60A tail.
Of course on even the best 14500 cell, you get a healthy drop (1387 lumens @start, 1234 lumens @30 secs), as expected (low capacity cell and not much available heat sinking in such a small light). In the 1,200 lumens range coming from such a small light is pretty stunning though.