I'm with FS, Load2n, and Randy !
The car may not be designed so that wheel's ride upon the center guide strip of the track. . The big word is upon as FS points out.
You would think that the rule on wheel spacing across the body would also rule out.. insetting the wheels to ride up on the guide strip of the track.
All car's will at some point make contact upon the rail as load2n also points out.. whether it be in a controlled manner or an uncontrolled manner.
Due to the track as it may have some twisting to the left or right on the curve section or even some tilting in the flat sections.
( Wheel's to ride upon the center guide strip ) the word upon is just another word that has two principles its based on.. for on indicating a position reached by going up.
like climb upon.. make's me think of rail road tracks and how the wheel's are designed run.. and ride upon the rails of its track.
However could the rule interpretation.. also imply that they don't want cars.. with a lifted wheel in its design.. that could ride upon and over the guide strip.
Causing the rest of the (wheel's) on the car.. to do the same while leaving the track. ( as Randy point's out also!)
Id would say you need to ask your counsel for clarification on the wording of upon to there ruling.
because synonyms of the word upon are
on
against
next
alongside
upside
next to
And then even ask the question.. of what the center guide strip on the track are for.
guiding the wheels on the car and so that the car can travel, roll / ride upon the track surface that should even include center guide strip.. as the intended purpose of having them on a track.
Just some of my thoughts..
However you will need to ask for clarification.. as I have never ran across wording to a rule like this one.