I'm just throwing this out there.
I bought my 'C' new. It had to be ordered. When it came in. the dealer called me to look it over, but told me that they had work to do before letting me have it. They said the marker lights on the cab over are installed at the factory with power screwdrivers and its easy to create hairline cracks that leak. They removed the lights, checked for cracks (there weren't any) and resealed them. Over 10 years and no leaks. BTW, I only store some light weight stuff in the overhead. Nobody has ever slept in it.