With reference to Dry Weight, if you're referencing the Dry Weight as shown in Sales brochures, it's not worth the paper it's printed on.
Now if you mean the Dry Weight (Shipping Weight) sticker that's put on the unit just prior to shipping, that is at least a starting point as it includes all the factory installed options, but still no propane, water, vent covers, any Dealer installed options, or any of your belongings (clothes, food, pots, pan, plates glasses, DVD collection, etc.
With options, our RW arrived over a thousand pounds heavier than Brochure weight. So once you fill the Propane tanks, install heavier/bigger batteries and load it for long or full time travel you approach or go slightly over the GVW very quickly.
I think the newer generation of 350/3500 Diesel Duallies will handle rigs up to approx 20K. Our 2011 GM has a 21.2 Max 5th Wheel and a GCWR of 29.2K, so we still have some wiggle room.