I saw a 2009 Honda Fit in the metal for the first time a little while ago (yes, I live a sheltered life) and the very first thing I noticed was how the rear lines have really pronounced plan & profile taper:
The converging arcs suggest the beginning of a proper teardrop/airfoil shape.
Which of course led me to think: it would be an ideal starting point for a very organic Kammback extension to improve aero.