Thank you TC. I appreciate the offer to help. You are very, very knowledgeable. I can already see that I can trust your figures as much as I would trust my own. It's like I had gone out and done the research myself. I'm very impressed.
And like you, I want to have my cake and eat it too. I want to go places, fast, not spend any money, and have room for myself and a few things, in any weather, and not get rained on. Is it too much to ask?
The solution basically comes down to supremely minimizing Cd*A, maximizing GVM, minimizing parasitic weight, maximizing battery weight/GVM.
Then it comes to proof of concept. In the absence of a wind tunnel, the only alternative is the coroplast mockup, in the dead of night on a country road, a computer timed slowdown test, and weight with a truck weighing device.
And as far as shape, I can't believe that if Phil's CRX can get 0.19, I can't kick the *** of that with a custom design. I mean, have a look at it. The whole rear of the car is staring at me, quoting the lines from Spaceballs: "Suck! Suck! Suck!". There is going to be a huge turbulent vacuum back there pulling the car back. It's at least half the car's frontal area. If you eliminated it, surely you'd see commensurate Cd benefits???
After you've got a realistic Cd estimate, then it comes time to make a proof of concept. Obviously, this thing will be so far out there it may actually be easier to make a custom interior than try and use an existing truck/car interior to tack your "bodykit" on to.
So, it's either
a) find something that will fit the shell and give you a stock interior.
b) go with a strong chassis and build both the shell and the interior.
Perhaps something like a capri would be best from the perspective of testing. Since it's about as small a shape as imaginable, it would make a good test vehicle. Then you could either select something that was not bigger in dimensions than the bodykit you wanted to graft on and also had the right GVM, or go find a good GVM chassis, strip it bare and build your car from the ground up.