[morzh]

Because no rivnut will fit the thickness of both cap can and the fuse panel, I decided to use M4 copper pop rivets. M5 would not go through the fuse panel.
I bought 8 and 11 mm long ones.
I also used a M4 stainless steel washer to protect the phenolic fuse panel from cracking.
I also did not pull the mandrel all the way through, but stopped where I felt it flared the barrel enough to hold well, and then pushed the mandrel ouit.

Here is how it worked. I might use the pop-rivets and rivnuts interchangeably, depending on which one fits the place best.