As already mentioned I would imagine it's just a lot easier to incorporate square/rect. tube into the body..straight cuts versus trying to do rounded cuts around the A and B pillar...but other than that I don't see any reason why not.
My 3x3 tube is 3/16" wall and seems plenty stout enough.
My 3x3 tube is 3/16" wall and seems plenty stout enough.


i'm going to add a lip at the door frame so that i can go doorless like a jeeper. 