Well, I have debated that too. Do you partially close the awning when a storm approaches? Problem is when we get in rain storms here the wind blows and that awning acts like a sail and I fear it'll rip off and damage the trailer. Also, with the awning open, no matter if fully open and much more so if retracted partially I have been unable to keep the arms positioned with any type of angle. No matter how tight I make it, the arms eventually un-compress and it goes back to both arms upwards which then collects all the rain towards the trailer. Already once I've sealed where the awning connects to the trailer yet it still will drip water down on the slide underneath in strong storm.
A slide topper would be way better if it was possible. If it wasn't for the $85-$90 freight shipping charges I would order one and see if I could make it work, but that's a lot of money to find out it won't and have to send it back.
When it gets windy, I retract my awning to just cover the slide out. And, I don't really worry about rain pooling on the awning. If pooling is a concern, I would extend the awning to dump the water then retract it again. I have a slide topper over the main slide and rain pooling has not been a problem.
__________________ Harold and Cynde
2013 F150 S/C 4x4 Ecoboost, 3.31 Electronic Locking Diff - 10 speed trans.
2014 Winnebago UltraLite, Chasing trains where ever we are.