thoughts on "one door" design
I really like the tarp and how tight it sets up. Also, I like the idea of fewer stakes to finagle.
A thought on the setup:
It would appear that with only one "door" per end, the pitch is critical. It would seem to me that if the pitch isn't right within a few inches, the "doors" will not match the end opening and either you will have a bigger gap or the doors will overlap the sides. The latter isn't as much of a problem, but if the doors aren't big enough for a wide pitch, you are going to have gaps. Setting up and getting the pitch "just right" could be problematic at times. It seems like it would take a lot practice at different sites to get the knack of judging the pitch just right for the "doors." The "doors" seem to become a limiting factor then in the setup. Also, if the "doors" are too big and overlap the sides, either you will have to arrange for different tie-off points between the "doors" and the sides or you will have flapping "doors" in any breeze.
If the above really isn't a problem or can be overcome in the design somehow, then I think you have a real winner there.
With 2 "doors" this wouldn't be as much off a problem since the "doors" could be designed for a really wide pitch and then overlapped as the pitch narrowed.