Thanks for the tip.

I tested the GT Mini short tube + GT Mini tailcap and screwed it on the EDC18 = it worked without any modification on my EDC18.

The EDC18 tailcap doesn’t screw properly on the GT Mini short tube though (doesn’t seem to make contact), so I had to use the GT Mini tailcap instead.

Similarly, I could use the EDC18 tailcap + EDC18 tube and screw it on the GT Mini head, and it appeared to work properly.
(to verify: EDC18 tailcap doesn’t seem to screw properly to the GT Mini 18650 tube?)

What I’m not very sure though is whether the GT Mini tailcap+short tube, when screwed on the EDC18, will be too tight for the 18350 battery (my 18350 battery got compressed/dented by the Astrolux HL01 short tube already…)