Nice camper but I think he hit the 2 key instead of the 1 key when he was typing in the mileage numbers. I could see 12/17 if you kept your foot out of it and didn't have any big hills.
Pretty much my dream rig- depending on the interior layout of course. Best of all when the 7.3 gives up the ghost it's an easy 5.9L conversion- and 50 state legal!