I got sick of my Fiamma Awning flapping in strong wind and being told that I could only fit a single Fiamma curved awing to it. My fix is removable every time I pack up and is very easy to fit, it will also work on most Thule awnings I believe. Just get a 1 metre piece of 4×2 and fit the fitting in the middle, then got a 200mm piece and drill a 10mm hole in the middle, fit it as shown in the picture with th large piece in th channel against the van and the small piece in the outer channel, the tension th th rafter will keep them in place as long as you do up th knurled nut.

I have the same problem even with all the accessories, food for thought
thanks
Graham