Last summer I installed a partial boat tail, if you can call it that. wings down the side angled in at 12%, a kamback, a small front dam, fender skirts, a grill block, I also installed my spare tire on the front bumper, I tested this on a 1000km run with basically no change in mpg still on or around 16 mpg. I have since installed skirts between the front and rear wheels along the sides and started a belly pan these are not tested, I removed some mirrors and the roof racks, but installed a small chimney for the new heater on the roof. The van handles much better and is quieter, I find myself creeping up around 90-95 kph where I used to be comfortable at 80-85 kph.
any advice or ideas greatly appreciated