Final looks.
I also tested the rake angle impact and it was big.
+1,0 degrees gave delta Cd +0,0147
+0,5 in most calculations
0,0 one run delta Cd -0,003
So at least in the Audi A2 0,0 seems to be the best. For future it would have been best to start with that rake angle optimizing and after that the roof spoiler and diffusor angles.
That curvy dip diffusor does not work in the A2 body at all. Tried also to add curvy extension and that did not help either. Straigth seem to be best for this shape.