yet another spoiler question...

[Joenavy85]

with that much fender clearance might as well have the wheels fully faired in

[aerohead]

I can only recommend using the Aerodynamic Streamlining Template as a design tool for the spoiler.
The pure cantilever wing might create a safety hazard for pedestrians walking by the car.Ouch!!!!!!!!!!!!
If you went ahead and did a short tail( 12-inches ),extended the c-pillars on out along the Template line,then filled in between with your original horizontal wing plus one high ( as a wing/shade )and one mid-wing (also straight back from the glass) you'd be looking at a 4-mpg gain.