Gary, I would start with exactly what you just said. The single biggest change will be the Airbags on the truck. A Dually doesn't normally need the bags for weight carrying, you're doing it for suspension control.
Without the bags, and with a heavy pin weight like the RL has, when loaded if you look at the distance between the rear axle and the hard delrin snubber, you've only got about 2-1/2" till the axle makes contact with the snubber. What happens when you hit a bridge joint or a really bad section of roads is that the truck is coming up as the trailer is coming down and very quickly you run out of suspension travel and hit that snubber.
Something has to give, and at that point it's the truck and you get a sometimes violent up/down back and forth motion in the truck.
The Airbags replace the snubber. Now, you've got almost 5" of loaded travel. More importantly, you have the ability to control the rate of compression of the suspension by how much air pressure is in the bags. That's why you want to spend the extra $$ and have an onboard compressor with the incab wireless remote. When we're in a really bad section like I10 through eastern Louisiana or i95 in South Carolina I may change pressures in the bags three or four times till I get the ride I want.
For a huge improvement in unloaded ride of the Dually, add Sulastic rear spring hangers at the same time. You won believe how much better it rides around town without the coach.
Next, if you're going to be doing a lot of traveling, make the appointment at MorRyde in Elkhart to do the IS suspension and also disc brakes if you don't have them already. You will not believe the difference both in the handling of the coach but also the ride inside the coach. Very little if anything moves around. We don't even take the coffee maker or toaster oven off the counter anymore. Over 42k miles on the suspension and zero issues or worries. Well worth the $$$$
