FInally got the tender pickups done. Used a whole length of EE's 0.35mm phosphor bronze wire to give me these fancy springy coiled backscratchers
They are soldered to two bus bars made from double sided copper clad PCB material (thanks JZ for the offcuts with your sleeper panels!) These were low melt soldered to the chassis frame on the underside then the pickup springs soldered to the top.
Took a lot of fiddling and repositioning to get them right, you can't see it but the ends where they come into contact with the back of the flanges are doubled over then cranked ever so slightly so that the curved end where the wire bends over is all that touches the wheel. This reduces the friction to a minimum.
They still make a bit of a racket when the body is on. Will experiment with foam etc to stop the body resonating and acting as a sound chamber