I'd be worried about the wall not taking the weight of the longer awning. I know it's not as pretty, but I got a 10'x10' canopy from Costco similar to
this for more shade. Of course I wanted it for over the table a bit further away from the RV, but it could be a low cost option for more "awning" without any concern of the structure of the wall of the RV.
Yes, I do know how half-a..ed that solution is. But RV walls seem so flimsy to me, and the forces of wind on an awning make me feel like I should mention it anyway.