[moorecomp]

The best outlet is one which will allow the exiting airflow to be as close as possible to the direction of the external airflow. In other words, the exit air should be as close as possible to parallel to the direction of travel. It would seem the "backwards" NACA vent would provide a good direction for airflow, but the way it would be causing the air the constrict in the reducing width slot would induce turculence into the exit airflow. A similar design of just a simple rectangle would seem to be better..