I have a 33' 1993 Dutchmen 5th wheel that is in need of some siding patchwork along the front driver side (over the portion of the trailer that sits over the bed of the truck). I have my siding pieces but I don't see any "studs" to screw into. Under the siding I see a sheet of 1/4 inch plywood over 2" foam. If I pull the foam back (carefully) it looks like their is another piece of 1/4 inch plywood and then my interior wallpaper. Is there a common layout of the frame? Is there always studs running vertically down each window? Any help would be great. Thanks!!