Originally Posted by rex
...are the support beams between each window? we are envisioning 2X4's screwed into the side of the bus at the beams and the roof structure being constructed off of them, rather than relying on the sheet metal roof for any support.
That strategy has been done many times and so I assume it works. Look in the photo gallery at the "Ragbrai" buses. They all have roof racks and many of them did it how you are proposing. The beams do go up between the windows and continue over the top to form a hoop of sorts like a covered wagon. I think the question before you now is whether or not to have the crossbeams supported in the middle of the roof, or have them elevated so the weight is only on the sides. I don't know the answer to that question, so perhaps others will chime in...