Made my own "Rope & pole" style awning recently and gave it a check out on my recent trip to Mono Hot Springs. Only needed a few tweaks which have been done and should shore it up nicely.
I purchased all of the supplies, including the awning rail, fabric and the poles, at sailrite.com Total was about $235
I went with the flexible vinyl awning rail and gave secured it with VHB tape only at this point. I was advised by Sailrite that this was an acceptable method and that it should hold without putting holes in my roof. Time will tell. rope & pole are not meant for windy conditions anyway. We did get some wind and rain at Mono and it held just fine. Worst case I can drop a few SS screws in at a later date if needed
We did not make our own awning (we puchased a Vintage Awning from Marty). But we have a similar setup. I riveted the awning rail to the trailer, at about the same point as yours. I put a stop on my drill bit and installed the first rivet inside the closet area, to make sure neither the hole nor rivet punctured the interior insulation (ours is the old "elephant hide"). As I recall, the rivets I used were 1/4" in depth.
That is a really cute awning. Thanks for the resource. I'm working on a plan to create one for my little Scamp.