After considering for about a year how to construct the walls of the cabin, an acquaintance suggested during a long telephone conversation that I simply use a 30mm facade sandwich panel as an insulated outer wall or top layer and insulate the inside, with the advantage that cables and pipes could be hidden in the wall.
I found this idea very appealing, especially because I could then install a cozy wooden paneling inside. But then I saw two or three reports from overlanders whose vehicles had rolled onto their sides. In almost all cases, the cabin hadn't been badly deformed. 
Therefore, and also because I had become reasonably proficient at welding by then, I decided to construct an inner frame to which I could glue the sandwich panels. Furthermore, this had the advantage that I could also weld the substructure of the furniture from steel, which would naturally stiffen the overall frame even more. 
