Will 4 wheels on a model locomotive provide enough pickups ? I don't think so and with another 6 to choose from on the C15, I ought to be able to do better.
At the front, the bogie is attached to the body rather than the chassis. If I try and wire that up there will need to be provision for the chassis to come out and disconnect. Maybe something involving micro plugs and sockets or very long wires might work but both seems a lot of trouble. Fitting invisible pickups on the thing would be a challenge too.
The pony truck at the back looked a better option. It's bolted to the chassis and flops around so will stay on the rails nicely. I added a load of lead to the nickel silver - not that easy as you have to put the cutouts in to access the chassis retaining bolts - to improve road-holding.
Electric collection comes from a couple of PCB off-cuts with phosphor-bronze wires. These have the added advantage of providing some side-springing to the keep the axle centred in the narrow truck.
So now 6 of the 10 wheels are doing something useful. Let's hope this is enough.