Charlie, the first time I saw the 21' I thought that awning placement was kinda "weird." It "should" have been placed further back, when viewed from the outside. But you know what? That back arm is placed EXACTLY on the rear window seam. If you're inside and the awning isn't deployed... you can't even see it. Truly!
I was astounded, but have spent a lot of time inside Dave&Kathie's 21' and it's true!