I love the 18500 tube on the fw3a series.
I use the Panasonic 2000mah cells and they are more than fine for the type of light and its uses. Be honest, FET is for fun on the fw3a.
I would actually estimate it does far more than 4a. I’m running mostly high cri emitters in them, but I can’t tell the output difference with the FET,maybe the tinest.
This setup with say a 219b/c is my favourite edc home light. 15mm drop in length is worth dropping 1500mah much of the time. 2300mah drop to an 18350 is too much.
I would love to see more 18500 lights. 18350 cells just don’t last long enough to me.