License plates from truck to TC and back again, and again.

What about rare earth magnets embedded in the plate frame holder? If a plastic bumper, perhaps matching magnets somehow inside the wall of the bumper.

The ones I am using to hold the siding to my camper while the glue dries have a 55 pound pull each.

Yeah yeah, theft and all that. But if they didn't know you were using magnets, they would probably think the plate was welded on when they tried to pull on it.