You said there are pickups on all wheels but two have traction tyres. Bit unusual to have pickups on these as they are insulated from the track. Are they making the noise perhaps?
I reckon you want the rivet head on the outside, is that correct Fazy? You really can't fix a rivet in place with the valve gear in situ, I would have thought that is impossible.
They'll be in that safe place you put them in poliss. I bought a set of router bits a few weeks ago because I couldn't find the ones I'd put somewhere. I thought 'I know I'll put the new set somewhere where I'll remember where they are' so I did and that's where I found the ones I'd lost.
Nice work Jeremiah. I dare say in the not too distant future we'll all own 3D printers, they'll be as cheap as ordinary ones. What is the dimension of the coin?