I think for a single-occupant vehicle with quite minimal cargo capacity, the overall package could be smaller. And as one who lives in a windy area and knows that rarely does the wind line up with the road, I'm always considering the effects of crosswinds as the vehicle will almost always be in a x-wind condition to some degree and hardly ever at 0 yaw. Thus I suspect pontoon fenders to not be an asset (I wonder what the Aptera boys have learned about that).
As far as eyeballing the Cd... I'd say greater than .15 and less than .30.
To me it seems like the VW 1L would be a good thing to copy as they have put real and significant engineering development into it, and have the proven results.