Don't you effectively earth it anyway when you put the stabiliser legs on the ground....... It's been a long time since I was taught about faraday cages, but if I remember correctly it works in cars and planes because for all intents and purposes the fuselage or body of a plane or car is essentially a large tube with the occupant sitting inside, well insulated (normally) from the electricity, a camper is far from being a tube especially with tent bows sticking up in the air, in comparison to the distance that power has already travelled, the distance between the camper and the ground is almost inconsequential and would jump that gap easily.......
On a slightly different note........ I was Ice Climbing in the French Alps once when an electrical storm came through, it really is not fun when you start glowing and your Ice axes start kind of humming with all the charge in the air..... Make you feel very very small all of a sudden
