Awning on rear window

I have a large 7' wide awning over my rear window. It is the Carefree brand, just like my main awning and other window awnings. Since it was installed as a factory option, I am guessing that the rear cap had wood, or some other material, molded in to the fiberglass rear cap to accept the screws used to mount the awning.
You might check and see if an awning was available as a factory option on your coach. If it was, you may already have all of the back-up needed to securely mount your awning.