Your camper looks great. What kind of sheathing did you use?
Another easy way to squeeze more mpg is to advance the timing. On engines with an actually distributor I would advance them until it dieseled after the ignition shut off and move it back 2-5 degrees.
If the truck has an OBD-II (post 1997 vehicles) Bully Dog Tuner set at 87 octane and reset the timing 2 degrees or so.
2012 Nissan Frontier 4.0 V6 - pre mod 19.6 mpg, last tank 23.25 mpg and current tank with timing adjustment is at 30 mpg on scanner.
