I would like to play devil's advocate for a minute. I'm speaking Chevy now. A 3500 srw with 18 inch tires. The 3500 dually comes with 17 inch tires. The 18 inch tires has a load range 400 lbs each more than the 17 inch. If you lost one of the duals unnoticed you now have one drastically overloaded 17 inch tire. The next thing is for slippery roads the lbs per square inch on the rear axle with the srw is much greater than duals.
We have a dealer in London ON. selling Mobile suites who advertises bring your truck hook on and see how things look . If it looks good take for a test ride.
I have a 15,000 Montana on a 2500 HD Chev and it sits perfectly level with no air bags and no helper springs, just a stock truck. I have seen numerous dually trucks with headlights shinning in the trees.
The truck weighs 8000 lbs and the trailer 15000lbs and that is 53% of the weight of the trailer. Only the RV industry could sell that picture and some profess we need more truck. Just something to think about.