Just for fun I put an 18500 cell in Convoy S2+ only with the empty head, tube and tails (with switch and spring) and the battery top is above the limit of the threads.
This means that to use an 18500 in a S2+, you need to have minimal threads on the pill and very short springs (or even buttons) both in the driver and in the switch. Even that way, I am not sure if it will fit and work without damaging the cell or the driver and switch due to the pressure.
If you want some inspiration you caan check these posts and threads:
g_damian:
CRX:
Firelight2:
MascaratumB:
There were some old posts from comfychair but I can’t find them :zipper_mouth_face: