One reason that class "C" are over loaded is that the manufacturers use the smalles chasis for what they are building, they will use a F-350 to manufacture a 22 footer and use the same chasis just enlongated and then proceede to add all sort of goodies like heavy counters, tile, and then they add a slide or two.
Some of the rental units that are being manufatured today are using heavier chasis as in the F-450 and no slides, you also have to consider what else do you carry in the RV, cast iron pots and pans, havy plates a whole set of glasses and beer mugs and all sort of goodies, and no one takes into account the wheigt of the persons in the RV.