The biggest thing to prioritize in my mind is to make sure you maintain a border (partial wall) around the rear doors, like GPW shows in his sketch. This border is basically equivalent to the shear wall, the same as a TD bulkhead, that provides all of the strength at the rear end that keeps the walls and roof from racking, especially from the weight of the side swinging barn style doors when they are open (no matter how light you build them). Consider that little panel frame around the back is the only gusseting you will get in a true (empty) CT, but a 4 or 6 inch gusset is way better than no gusset at all. This will keep your doors from sagging, keep them sealing well and latching properly with typical hardware store hardware.
If you look at a tractor trailer "van" trailer or box truck you will note that they don't have this feature. It allows for a bigger opening and avoids the potential of having a fork truck wipe out the wing walls. However, these trailers can be quite floppy when the doors are open. If you look at the way the door latch works, they have cams (or toggles) that lock the tops and bottoms of the outer flap door in rigidly (at the opening edges) so that the doors register together in the jambs and become the shear wall when underway.
Even enclosed car hauler trailers with folding ramp doors and not much of a door flange will usually use the same style of top and bottom bar latch (can't remember the trade name for it ATM).
Here's an example. You can't really make out the cam latches at the ends of the pipe, but they are there inside of the aluminum sockets that get mounted to the box.