PS: Have you spent any time on TruckCamperMagazine.com? There are a number of articles on expeditions and lifestyle stories that would be good reference for you if you haven't. The link for the trip Brad Christ took in our rig before we bought it is
here. I have a few photos from Brad he sent me when I bought his rig, but my favorite 'spooky' one is in the article above. Looks like good girders under there, but a lot of space between them and those steel sheets look a little to few for comfort...
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On edit, YIKES! I now see the photos of your camper and rot issues. That's tough. I'm not so sure I'd say "just roll with it" after seeing the pictures.