Length, Width, Clearance
  1. The car width at the wheels may not be modified. It must be the same as the original kit (2 3/4 inches). 
  2. The wheel-base (distance between the front and rear axles) may not be changed from the kit body distance of 4-1/4 inches.
  3. Overall length may not exceed 7 inches.
  4. Overall height may not exceed 2 3/8 inches.
  5. Bottom clearance between the car and track must be a minimum of 3/8 inches so the car will clear the center guide strip on the track. 
  6. The width between the wheels must be 1 3/4 inches so the car will clear the center guide strip on the track.