[Cd]

AeroModder, have you tufted your car yet ?
I'm guessing that you are having a lot more turbulence at the back glass versus the Fusion, due to the steeper angle.

Are you positive that the flow is re-attaching ? ( I'd guess yes - but that not enough of it is re-attaching to really make a big difference. )

I certainly do like the look of it !
If you're not seeing much attached flow, I wonder if it would be beneficial to raise it up several inches to where it meets the rest of that airflow.