Thanks. Thats what I was guessing but the little piece of wood mounted on the side seemed like it provided no support and was lower than the other side. Looks like the arm would be at an angle towards the walls unless the foam keeps it in place.
I have a '97, 25' Safari and they are set up nearly identically to those that I have seen pictures of on this thread. Looks like it must have been a standard way of installing them across many models and years.
1997 25' Safari
2012 Chevy Silverado HD 2500