I guess I'll chime in since I've got the largest rear wing around
I've found that even at 60-70mph when the bug was at the limits, those limits were lower without the rear wing on my car. Over 100mph got sketchy very quickly going into braking zones because the rear was already sooo light. With the wing the car stays planted and the faster you go the more you notice the stability. Since your intercooler relies on airflow over the back window I'd suggest running a single or dual element wing, even with the top of the back window and over the vents vertically. That's how I've got mine setup and I can speak for it's effectiveness.
