Very nice. I also occasionally build a 1:6 or 1:8 scale open wheel race car. I use 1:6 scale for midgets, 1:8 for sprint or Indy cars. I use various materials- some aluminum for flat sections, vacuformed styrene or fiberglass for compound curve stuff. I guess I am too lazy to beat out aluminum :-)
I did sell one midget model. After a photo appeared in a magazine, this guy kept bugging me about selling it- finally broke down and sold it to him. But I mainly, like you, build for my own collection. I also occasionally build in 1:12 scale. I do these entirely in wood, except for wheels and tires which I cast in resin. I built a series of 1:12 pre-WW2 midgets, have only one left- other three donated to museums.