I posted a fresh article at MetroMPG.com about the "Kardboard Kammback" described in this thread.
(And yes, I realize it's not technically a Kammback
)
In it, among other things, I outline the reasons for grafting cardboard on the *** end of the Firefly in an attempt to mimic the shapes of these slick hatchbacks:
FYI, you are forgiven for not recognizing the car on the right. It's the 99-05 Audi A2, which of course was never available in North America. With its at the time world-leading Cd for a production car equal to that of the Insight, the TDI version of the A2 was rated at 3L/100 km, or about 78 mpg (US).