Supporting a pop up roof - examples or methods?

If you can remove the arm with the roof lowered, problem solved. The lower shell of the camper supports the roof.

Otherwise, good old fashioned American 2x4 lumber, cut to the proper length, is how I'd do it. Build a temporary wall out of 2x4's. Couple of studs, a top plate, and a bottom plate. The plates spread the load out.