This whole thing is quite confusing. The Traxxas TMAXX and Revo are both 1:10 scale but run monster truck wheels. They have a different chassis design to the CEN but really it's the wheels that are the difference. The required wheel dimensions are specifically designed to remove the possibility of trucks with 2.2" wheels qualifying to race. Even the new Proline Moab tyre is 5" tall and 2.25" wide and they are the biggest 2.2" sized tyre I can find.
It will take a change in the rules to open the window for CEN and similar trucks to race small block. The problem is that I cant see that happening until the "my Revo's faster than your Revo" class, gets boring for the competitors.