We wanted more food storage in our 2017 R Pod 178 so we added a cabinet. The concern was the load on the wall but it appears to be holding well after towing almost 2,000 miles during our recent trips.

The attached photos show the finished cabinet and various stages of construction plus the dimensions. The frame is 1/2" oak, the walls and doors are 1/8" plywood or hardboard. 

One concern was inserting toggle bolts through the cabinet into the wall. Instead, two 3" x 1/4" pieces of oak are mounted to the wall and the cabinet screwed into them. The wall is 1/8" board with compressed styrofoam insulation behind it. After drilling the holes for the toggle bolts, I chiseled out the insulation with a wire coat hanger bent to 1/2". This allowed the toggle bolts to expand in the wall.

The latch you see in the photo did not work - the first time the camper was pulled, hitting a pothole caused the latch to pop up and the cabinet emptied out (it contained only a few light items - we weren't sure how it would perform so we kept it light). We now have a bungee on it. A spring latch would be better.

We have since loaded the cabinet with heavy items and it's doing well.