That's not the most efficient design for a boattail since it has only vertical taper. The most efficient boattail for an aircraft has equal amounts of vertical and horizontal taper. The most efficient boattail design for a car would have more horizontal taper than vertical taper. This is because the presence of the ground surface limits the amount of vertical taper you can efficiently use on the bottom side since it limits the movement of air to fill in along the bottom side of the boattail. My boattail has equal amounts of vertical and horizontal taper and terminates in a 2 foot wide horizontal line since my car is wider than it is tall. I kept more vertical taper on the bottom side of my boattail than is optimum since I have a steep approach to my driveway and I didn't want to risk the boattail dragging the ground.

If you look at the boattail designs from the 20's and 30's (Rumpler Tropfenwagen, various boattail speedsters), they had predominently horizontal taper.

It's funny, I have a chance to get those exact same wheels for my car! pretty neat car, and not bad looking

Basjoos - I don't know if you watched the video but the lights are only exposed when they need to be on. Otherwise the center section rises up to fit flush on the front of the car.

The Fiero isn't a lightweight. A Spitfire would be a better starting point.

What kind of mileage would it get with a VW TDI engine?

The original body design of the Fiero has a Cd of 0.37, so it's not that very aerodynamic (even worse with the headlamps popped up: Cd of 0.41). The notchback rear window creates a fair amount of drag and the pointed front end rams a lot of air under the car. The 1985 GT model was redesigned with an aero front end and a rear spoiler which brought the Cd down to 0.35.

But just for your information, I've gotten 38 mpg in my old Fiero @ 55mph with the 2.5L engine, automatic.

This 100+mpg car looks absolutely sweet. Shockingly it's very similar to what I would invision an ultimate aero machine to be like.

Oh yes they do. Ask any pilot of an taildragger about the thrill of trying to set it down on a runway in a gusting 25mpg crosswind without ground looping. But to get back to cars, my boattail has increased my car's sensitivity to crosswinds only slightly.

TomO - I watched the video from work. I live too far in the boonies for DSL or wireless. Dial-up and video do not a good match make. I have never been a fan of pop-up headlights (too much drag and one more thing to break in older cars). I don't know why they didn't just have a clear cover over the headlights and dispense with the pop-up. One inaccuracy from that TV commentator. He was saying that this car can do 0-60mph in 5sec and also get 100+mpg. What he didn't say that you can't get both from the same car/ICE combination.