I am not sure if I understood you well LB, but the OWM doesn’t work with other 18650s, long or short, if they don’t have dual polarity in the head.
I posted this photo in my review:
The spring is for the + and the ring with 3 “pins” is for the - of the battery.
To be precise, in case you want to use just the side switch you can even cover the bottom of the battery.
Although, for the tailswitch to operate and charge, it needs to be uncovered.