Don't know about MHs, but I do know someone who did them to their truck camper. The MPG difference is neglible, the biggest gain with them was keeping tbe back of the camper cleaner, but that was about it.
'92 Dodge W250 "Dually" Power Wagon
'74 KIT 1106 Kamper Slide-in Truck Camper
'06 Heartland Bighorn 3400RL Fifth wheel
Follow along with me in the The Journey of