I'm going to get a second shade for our awning on the slide of our 5er. A couple of suggestions based on the experience with our other awning:
Get one that has a zipper down about 3 ft. from the top, this way you can unzip and retract the awning without having to remove the awning from the track is case it has to come down because of the wind.
There are different opacities, decide how much sun you want to block and choose accordingly.
Take a measurement with the awning open (awning to ground) and take off half a foot or so, this is the "drop" measurement, as indicated above you can move the shade out to make small changes as needed.