No solution and its getting to the end of the season up here, so will deal with it next year. Likely go w/ some variation of what you’re proposing:
1) exterior 2″ antenna mounted on the roof of the camper via a 13″ sheet metal shield, coaxial passing thru an existing port (or thru the refrigerator’s roof vent);
2) booster mounted in the cabin of the camper;
3) an inside patch antennas mounted near the front of the camper’s galley (hoping that it will have enough strength to reach the cab of the truck).
Look forward to hearing how it works for you.
2006 Ford F-350 crew cab, utility bed, 4WD, DRW
2007 Northland Polar 860