you prolly have to use a punch set to mark a divot in the cap from the inside. then drill from there.
I am thinking about making some more of these myself.
nice work.
actually I think that the inner small tubes were adjustable capacitors soldered to the baseplate.
they seem to be at 60 degree angles pointing outwards.
let me see if I can dig up a screenshot.
the feet for the tubes also has a curve in them, or actually goes into a hole in each cell.
Woah! take a look at these!
you can find more pics
go to the blog