[aerohead]

Originally Posted by Vekke

http://wwwm.coventry.ac.uk/researchn...%20Vehicle.pdf

Good test documents on drag reduction

So if the production car comes in at Cd 0.288,and the tail nets a 10% improvement in HWY mpg,then that's a 20% drag reduction,and 0.8 X 0.288= Cd 0.23.
If the integration of the tail to the A2 was tighter we might expect to shave a little off that number.