OK, since I have no life these days,
here are the pics ya tried to post.
Yer car I presume
The SUV sample pool
And the one showing it sticking up about an inch.
To answer your question as best I can, this type of spoiler will only serve to keep your back window cleaner at the expense of creating aerodynamic drag.
If you want to improve the aero efficiency, you'll need to do something like a "Kamm Back" to smooth out airflow as it leaves the back of your car.
I'll post more later, and I'm sure others will chime in, now that they see whats goin on in Bee eye tchville.
