Actually, neither.
I filled the slicks with A+B Putty and drilled holes into both of them. I inserted a metal rod into the holes. Then I drilled holes at an angle into the mounting base to match the metal rods in the tires. I had to glue the rear tires on really well, and I got the angle a little too steep compared to the photo, but it still works.
The photo below shows the pin on one side. I need to touch it up with some black paint before I show it at a contest.
The good thing about this is I can take the pins out and display it flat and then judges can look underneath it.
And oh yeah, there isn't any driver in the car, so it would have to be a paranormal event to get the wheels up like that.