The stamped floor pan is where most of the strength of the unibody is. Sectioning the tubing into the floor and fully weld it, as opposed to a couple of inches of attachment in the front and rear, makes a big difference. I also like to see the cage attached to the inside of the body in strategic locations, rather than just sitting on the floor pan. Make the body shell one interconnected unit, top to bottom, where the pieces all strengthen and support each other.