Depending on the manufacturer of your rig, there may not be studs in the walls. My Eldorado Aerotech has a fiberglass body that doesn't have any internal skeleton like the metal body buses do. The steel body school buses are built like tanks but with all those rivets there's no question where the supports are.
The inner fiberglass wall on my bus holds a screw really well. If I don't drill my pilot holes large enough it's easy to twist off the screw head.
We're very visual here, we....must.....have......pictures.