And here are some diagrams with dimensions. Most all dimensions measured with a micrometer. There is a small ridge around the circumference for seating in the tube, I am guessing at these dimensions. I tried my best to make sure these are correct but I don't guarantee it, if someone measures different please post. The top cap is three pieces, the metal part, the rubber center pin grommet and the center pin.
Used a SS tube to pull the top cap off, pulled out the half moon plastic piece below the circuit board then pulled out the circuit board then the button tops fell out. Window is plastic and presses out. Soldered new top cap on to circuit board, set buttons in tube, inserted circuit board then plastic half moon, pressed together in a vise using wood pieces on either end, then inserted plastic window to reassemble. Very easy.
The top cap is chrome plated brass and has a small flat head Philips on the bottom side with a dap of solder for soldering the ground lead. I do not know the size of that screw. Hot lead solders to center pin which also had a dob of solder on it.
I had to replace the top cap on my V3 and got an extra just in case my V5 ever needs it. These will fit all the VAMOs but is threaded for a collar ring like the V3/V5 has. Purchased parts from ecigarette impressions.