Gotta hand it to Johan Bosman on this one... look at pg 5 of this pdf:
http://www.streckenflug.at/news/js_c...on_2010_07.pdf
Personally I think his take on the exhaust vent is simply ingenious.
The opening on that thing is immense and has got to allow much air to
pass, but flow is organized by that little louver/wing. Pure genius.

I may just be preoccupied on the subject right now since I'm in the
middle of making vented ASW-20 hatches (Mandl and Butler styles) for
the upcoming 20 gathering at Tehachapi. Pics to follow...

-Paul