The people that are hit and killed by lightning each year were either the highpoint on the ground, bicycling or riding a horse or motorcycle, or standing by a tree or light post or under a metal roof. Inside a camper is a relatively safe place to be and you definitely want the jacks off the ground as far as possible. Use the rubber tires for insulation. Lightning will often travel horizontally until it finds that protruding object or person that takes it to ground.
Check the government statistics. It makes for interesting reading. The fishermen that were hit had left the water and were standing by the lake when they were hit. They thought they were at risk on the water but safe standing under a tree - they were dead wrong.