As to the question about elec awnings, yes they sag!! In my opinion, along with the undeniable fact of our new elec awning sagging, I really think that that the awning mfgs have lightened the tube, which leads to a weaker tube. I could "bounce" the tube up and down in the middle much easier than on the previous manual awning on our Jayco. It had less "natural" sag and and "bounce" than our new one.
There is still noticeable sag when the awning is deployed, but I have been trying to stop rotation of tube so that the sag is up!! Keeps the fabric a bit tighter that way. Don't really want to add any other styles of support like have been mentioned, since we boonie camp in the mountains mostly, and that stuff slows down retraction if hit with high winds or heavy rain suddenly.
Sag without the support:
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Just can see the support in this pic:
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