Having worked for a Helicopter company for 30 years I can tell you every door, window, access panel or cutout weakens the structure. This all has to be designed for by adding structure around the cutout area which adds weight to the aircraft. Large tapered pins could be added to the slide out that would fit into Al or steel fittings that would stabilize and support that large cutout while traveling. I have not seen this in any of the MH's that I have looked at. I would not doubt that hitting potholes would add many more G forces than an air craft would ever see in flight modes