We haven't seen 'thin' spots and our tt is over two years old. I do see the spotting and even when we clean it with a bleach based cleaner, you can still see a faint imprint of where the stain was.
We keep our non-adjustable pitch awning out only when there is no wind and we are there to bring it in just in case the wind does come up. The awniings pitch is too high for us to try and tie it down (unless we drag a picnic table to each end which neither of us is willing to do).
Other member will add what they do to help with the stains. Good luck