I really doubt that'd help. If the tarp is pitched well, there isn't any slack in the door at all. On the contrary, the whole thing is drum tight. If the tie-outs were there, you could conceivably make a larger door with a third pole though!
Has anyone else found it fairly difficult to get a tight pitch when making a corner tieout the door? Will this be even more difficult with the cuben trailstar's lack of stretch?