Raising the roof line would leave a larger 'dead space' in the rear of the vehicle, and greatly increase DRAG. The current 'Kammback' aerodynamic rear style would be compromised because; “According to the classic definition the tail should be cut off where it has tapered to approximately 50% of the car's maximum
cross section “.
I get that this vehicle is a study of kammtails. However, the 50% you cite assumes symmetry. In this case, I'm not sure how the asymmetrical cross section effects that number. It could be that the ideal is 25% down on the top, instead of the full 50% reduction occurring on just one side of the cross section.
Anyway, wind tunnel testing would be of primary importance, and with the explosion of tunnels available, I'm very surprised I haven't read anything about prototype development being supported by a modeling confirmation tunnel session. Anyone found any mention of the aero design development process?