that's not much different than stock, the main 'laminated' strut across the top carries the weight, and is supported thru the divider post and the door posts front and back - I suspect the oil canning of your sidewalls was a result of the converter using too much heat to cut the window holes, like a torch or heavy use of an angle grinder .... and considering the brick wall aerodynamics of these trucks, I don't think a roof top load would affect things much
Bill
