[j-c-c]

To recap, it is a COE flat front 40' bus diesel chassis. 2/3 of roof will be Solar panels, front 1/3 will be viewing platform. I want a very comfortable single person living quarters in front portion. Rear portion will have storage as available and one vehicle, likely a streetable TA type muscle track car, which needs 17'. Car has approx 3' of rear overhang beyond rear axle. Letting that 3' hang over the rear RV bumper gains me much useful living quarters space.

My original plan was when car was secured for transport was to allow the rear car overhang to protrude 3' inside the rear 4' long hollow composite nearly full height "energy conservation device" sight unseen, and fully enclosed.
The Aero device would be top hinged to access and remove the car and become a shade for car Maintenace when car is on the ground, if desired.

Adding a small conventional tag axle is doable, but I'm starting to encroach on rear sided mounted aux genset, fuel supply for genset, existing bus fuel tank, and to be installed fixed interior sloping ramp.

As I'm typing this, I'm thinking I should just design the build with the option of adding a tag axle only if needed by enforcement down the road, and stay with my original plan and build the best looking, most professional easy to assume "approved" energy saving device and take a chance on a $100 overlength fine if it ever gets noticed.