Originally Posted by Seth_Horwitz
Most of the aero work on a car is composed of the underside (one of the largest factors that most people don't even know about), and the nose and form factor running up and over the car. The decklid probably gets very little airflow over it, so modifying it probably won't have much of an impact at all. That's why the GT cars have their wings so high off of the trunk, just to grab some air.
So what about the CF splitters people are adding to the front bumper?