Hello -
I took off the vertical coroplast you see above because it was creating a backpressure and making the AC work harder (the fan already scrapes, so you could hear it scrape even more). The top horizontal shade is still fine because there is no "pressure-venting". When I detached the lower part of the vertical Coroplast (a hard disk magnet), it angled out close to 45 degrees from the exhaust pressure.
I would like to put a lightweight "shady tarp" in it's place, but it would need to be fire retardant because the AC exhaust is very hot. I might retest the coroplast without the lower magnet-anchor to see if the backpressure problem goes away. I couldn't do that last time because I didn't want to leave my wife "stuck" with the problem .... Ding! I know, I'll just use S-hooks. Easy-on, easy-off.
CarloSW2