IMHO, nothing will really protect you 100% from a direct lightning hit. Even if you are enroute to a "safer" location, and happen to be under a tree that gets hit, you are in danger. However, I believe you are safest inside something that is low to the ground, so as to not attract lighting, and something that is insulated from the ground, like rubber tires. Lastly, if there is something that can act as a lighting rod to direct the current around you and into the ground, that would be better. I may be wrong, but logic says to me that a trailer on rubber tires, with a metal jack or landing gear touching the ground, would be about as safe as possible, so long as you are not directly touching any metal that is part of, or connected to, the trailer frame. Think of it this way, if you are in a car on which a live electrical wire has fallen, they tell you to not touch anything metal until the current is turned off, and you will be fine. Seems to me the same principle as in a trailer. Sorry for the rambling, but that is my humble opinion.
2003 Ford F-350 V-10 Crew Cab 4WD Long Bed
2004 Jayco Designer Medallion 29 RLTS 5th wheel
Bill, Gayle, and Mindi (dachshund)
Retired at last !
Nothing is foolproof to a sufficiently talented fool.