Here are some photos of how I closed the gap around the rear frame on our 8280WS Rockwood.
Plastic cover made to fill gap on the outside edge of the 8020WS frame
Another photo of plastic cover to fill gap on the rear frame rail of a 8280WS
Photo of caulking around inside edge of frame rail of the 8280WS
I hope this keeps the mice and water out from under the 5vr.