When the Aliner is folded, the box adds more rigidity to the sides of the unit. The cutout for the door considerably weakens the structure so with the roof not closed there would be considerable flexing of the box going over bumps. I actually added an additional hold-down clamp between the roof and door side of my Aliner so as to further reduce any flexing when towing.
I might move my Aliner with the roof up in my back yard or very slowly at a cg but never would go down the road that way.