Most RV sides are put into place by adhesive. Normally it is a Styrofoam wall between the studs.
Crane Composite is the largest supplier of material for siding. They have one product which is luann wood backing over composite Filon material. If water gets behind the wood will rot sooner or later.
They have a repair process, which involves either cutting out the whole section or grinding out the area if it is the size of a quarter.
I would go to that site and search under the support side.