[j-c-c]

It's a track/fun car, no rules other than safety. Air would be moved to the wheel wells. Car currently has a robust diffuser which might capture benefit/assist the extra relocated air's removal. Keep in mind, moving the airstream say 3in vertically 48" behind the roof line achieves my goals I believe. I already have two 1200CFM drivetrain/engine oil coolant exhaust fans sucking air directly from over the rear live axle, exhausting out thru the back of the trunk lid

Current typical large in line brake fans on the market move approx 400Cfm ea x2, but remember this extra airflow directed to the wells is only under braking, and only briefly under acceleration.
My thinking is a Plexiglas tube connected plenum with many small holes patterned across the upper surface of say an 8in extension of the rear roofline with its angle set to where I want the airflow to be directed, when the rear wing needs maximum clean airflow. Fine tuning wing height for this objective will be critical and maybe a bit of a compromise for the speed ranges intended.