Brian is on the right train of thought. The tent is not square however. but it's close. i want to say 44 vs 48 inches. I have it opening out the back (narrow width) to save as much room on the rack as possible other stuff. I would like to say I put more thought into it than that but nope, it was dictated by size. In Baja in March we ran my friends tent on a set of thule bars (4 if i remember right) and opened it sideways. you can see it on the banner of my
home page
there is one thing I have noticed is a huge benefit of it opening toward the back of the truck. sometimes the sheet/mattress get caught in the metal support when the tent is opening. when this happens it can't properly seat itself and thus is not flat. with the tailgate back there i can open the tent, lock the ladder in place, then set the ladder on the tailgate. with it properly supported i can slide the mattress forward slightly so it will not bind. then i lower the ladder to the ground. it may seem like a small thing but it is a big benefit for quick set up.
dmc