When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
In my experience, all vehicles built since the beginning of time have double-walled roofs incorporating an underlying supporting structure covered by a skin.
Without such structures, how could people in the snow belt keep from getting their cars crushed, or how could things roll over without getting flattened.
I've seen the OBS crew cab roofs and they are not smooth inside like the standard cabs. They use bows or trusses that are exposed inside the cab. I didnt know if the slantnose trucks were the same or different.