The boattail I built last fall on my 92 Civic was so effective, FE-wise, that I decided to make it a permanent addition to my car, replacing the Coroplast and clear vinyl boattail with one made of aluminum sheet and Lexan. I recycled most of the original aluminum bar framework in the new boattail and the new boatttail has the same proportions as the old one. I extended the car's cargo area into the boattail, so now with the back seats down, I have 6-1/2 feet of load floor (4-1/2" of cargo space behind the back seats when I'm carrying 4 people). I also installed a functioning hatch (the stock hatch was covered by the original boattail). I had the Civic off the road for over a week while installing the mods, during which time I drove our Honda Odyssey and Ford F150. When I first took the modified Civic out for a drive after a week's worth of getting used to driving "normal" vehicles, I was impressed by how differently it drove than your typical vehicle. Most cars slow down fairly quickly when the power is cut, especially at highway speeds, but the aerocivic only very slowly loses speed when power is cut. It makes a normal car feel like driving around with the parking brake lightly engaged.