Here is the Electrathon America rule regarding vehicle design: 2.0 CONFIGURATION 2.1 All vehicles must be three-wheeled (cyclecar or tricycle) or four wheeled. Any configuration is allowed. All wheels must be load bearing, and remain in contact with the ground at all times, even under hard cornering conditions.

Your suggestion is an interesting one and I imagine it was probably tried at some point which led to the current rule - somebody either didn't like it or deemed it unsafe. There used to be another organization called Solar Bike Rayce (sic) that promoted the use of solar power assist and encouraged two wheeled vehicles in a couple of classes. Unfortunately they disappeared a few years ago...

Over the years there have been teams who have tried "leaner" cars - cars designed with trick suspension and linkages to make them lean into the corners. A few have been successful, but most have mixed or negative results; they are usually fragile and unreliable, sometimes complicated and heavy.