I use several things to better secure and support my awning. One is the typical awning flappers that attach to the side of the awning fabric and then to the side rails. These reduce the awning movement along the sides of the awning. The second is awning roller tensioners like shown in
THIS LINK. These not only hold the awning down against the trailer, but most importantly keep tension on the roller tube keeping the awning tight. If you look close they lock into the roller tube rail and then pull on the awning roller in the direction of unrolling the awning and keep that tension on the tube via the springs.
The final is a support for the middle of my 21' awning in the middle that is basically just a adjustable extension pole it one of the standard awning light supports that slide into the awning tube slot that are normally used for hanging awning lights. I don't have the middle support for the awning tube when rolled up and rely on the rolled up fabic along the tube to provide that support when the awning is rolled up.
Larry