After finally spending some significant time in the camper I can now say I am extremely pleased with how it all turned out. Extra props for ATC for delivering a product of outstanding quality - especially in light of a very difficult custom build.
At this point the only thing I would change are the dimensions of the bench seats inside. I designed them around a certain sized container I wanted to store under them (through the outside storage hatches). Now that I have used the camper I know that the benches are too tall to be ideal seats. Knowing that, I would reduce the size of the storage a bit and reduce the height of the seats probably about 2 inches.
My thinking about this project has always been "what would make a good stock layout for a hypothetical production flatbed camper". With that in mind the sink-in-a-drawer didn't seem like an ideal final product feature (note that Marty came up with this to save me from my mistakes in planning). I've had inquiries as how I'd do this differently and after much discussion and thought on my part my conclusion is I wouldn't want to change any of the cabinet dimensions to accommodate a sink. So that means its either the SMEV I originally planned around and could not get, or the sink in the drawer. Despite its complications I do have to say I like my sink in a drawer a lot.