Well, if you tilt it too much, it can form a pool and if it rains more than it drains from the tilt and fills your pool.. Guess what happens??
Know that from experience..
Tilted my awning during a mild rain storm (first or second time out with the trailer back in 2002).. Tilt was too much to allow to drain off the end faster than it was raining.. Ended up pooling in the middle of the awning..
Luckily, I discovered it before it did any damage. Was able to drain the pool and looked at what happened and set the tilt about 'half' as much..
Rained just as much for the rest of the night and no pooling at all...
Worked for me. Been setting my awning at just a slight tilt from then on and have gone thru thunder storms and have never pooled my awning since then.
On edit, the only other way I have set my awning and not had it pool, was so keep both arms attached to the trailer and at it's lowest setting.. You can't open the door more than half way, but that also keeps the water from pooling..
Mitch