This camper shell assumes the rear roof glass can be removed along with the mid gate. It's finest feature is a 13 foot long full height walkway (6' 4"). Probably about 8'6" tall overall. Guessing a 20% reduction in range due to aerodynamic drag at freeway speed.
Drawings drawings drawings....
1. As aerodynamic as possible.
2. Stand up height (6' 4") behind the bed.
3. Uses the maximum legal length behind the bumper of 48".