I was in the process of winterizing our rig..The water pump is located under the bed and they have provided a small pullout on the thin plywood cover...When I got in a little closer I saw there was quite a large unused area to the right under the bed just perfect for storing gallons of RV anti-freeze and / or paper towels etc.. about 6 little woodscrews hold that part of the cover down I marked where a wooden strip support was and cut a 10" x 24" appx. panel. A couple of 1" holes for easy removal and the new access panel just lays in place.There are no elec wires..just the fresh water tank overflow plastic pipe so it is the ideal spot for more stuff!
I also installed a 12 volt receptacle in the outside water closet..This will be useful for a small air compressor to blow the water lines out if ever I need to or pumping up bicycle tires....