I added one to my Tetra-15 when I built it. it was really my only solution to vent cockpit air since the tailboom is sealed off aft of the wing T.E.

no arrows to direct the outgoing air, but I can hear it rushing out the vent, so it must work. no hard data for the numbers guys, that being said the guys I fly with in their german glass seem to think the Tetra does just fine, even with a hole in the fuselage.

Brad