Hi
You did a great job on it, I will tell you what i did on revell my 70 blue vette
1 the car look nice but handling what a nightmare, i had the same problem as you describe, even on plastic or wooden track
i put it apart, then cut the post and after, i put a Parma frame underneath of it, screw the body throught the parma frame,
and for the look, i kept the original Parma Wheel for the front and the back i use centerline for protrack( i got them thrued)
to look like low profile, aftyer all it runs great with no problem.
test 1 I tried from champion small wheels with spacer look like centerline, runs pretty good on a wooden layout.
test 2 i kept the original parma Wheel it runs better on both wooden or plastic track.
Sylvain