Anytime you hang a shelf, that will have to support some weight, you need to be concerns about the "meat" of the support wood. There's not much of that in our Class C. Your's may differ.
But here are some suggestions:
- build a frame. That's what I did for the shelves that sit next to the pantry in our wardrobe. There should be a post with pictures called "Pantry" in the Class C forum.
- rip some wood down to 1x1" and attach it to the sides/rear of the compartment. Glue and screws. This will create a bracket for your (now unadjustable) shelf to sit on