[morzh]

These caps, with a groove at the bottom, a the easiest to stuff.
This one is a dual one with both minuses connected to the aluminum can.

   
First cut off along the groove, closer to the top part, so the bottom has the narrower part left.
The top part should have the remnants of the bend removed, with deburring tool or exacto knife, remaining a perfect cylinder.
   
After cleaning and gutting, drill holes in bot rivets and an extra one.
   
Insert the stuffing, threading both pluses through the holes in the rivets, and the minuses connected together and then soldered to a common wire - through the extra hole.
   
This is how it looks from the other side.
   
After that, upon putting some epoxy, glue or JB Weld upon the internal walls of the top part close to the edges, insert the bottom part in it. It will go in as the narrow part still remains.
Why putting epoxy on the inside of the top and not outside of the bottom? Simple. The top would start pushing the epoxy off of the bottom part, so you have a mess to clean off then. On the other hand, if epoxy is inside, it is pushed inside and all looks clean, nothing at all to wipe off.