BTW, back to the flat roof (new version) ..
a few years ago that design (cross over poles) came up at Luxe Outdoor , so some clever chap suggested a way around the flat bit and this is how it was done :
Just a suggestion for the users of the first version.
(I had a play with one in my backyard just a few days ago.)
Add a tie out point right in the middle of the bottom seam on the non door side and stake that out.
It is not going to save the design but it will help.
I made that suggestion when I first spotted the design and trying it out confirmed the idea.