Not much into rules of thumb here but I do like to consider the overall towing combination, truck, hitch and setup, and trailer.
Airstreams have low frontal and side wind resistance, as well as full independent suspension and low center of gravity for stability. As good as it gets. Weight ratings don't consider these advantages over most trailers, they make an easier, more efficient and safer trailer to tow.
A high quality weight distribution hitch with separate or integrated sway control can equalize the hitch load on the truck's axles as desired and transfer some to the trailer's axles. Set up properly it can help stabilize the truck in turns, and ensures better braking. An Eaze-Lift w.d. hitch and two separate sway control bars are inexpensive and will do a good job. If towing cross-country regularly a ProPride/Hensley style hitch will make your towing life much more pleasant, if not your pocketbook.
The truck has ratings for load and towing, they are good starting points. You can improve it with good trailer and hitch selection as mentioned. The axle ratio can improve the power to the drive wheels, and you can improve the ration uses lower gears, changing axles, or a little smaller diameter tire if t has enough load capacity for you. On a truck a few years old you can improve handling, stability and ride by putting on new, high quality shocks such as Bilstein. Pay attention to axle and tire ratings, and use a truck scale to verify your loaded truck and trailer, and weight distribution hitch setup are ready to travel.
The easiest, surest and least expensive way to add safety margin is to reduce towing speed, less chance of trailer sway, loss of control in an emergency maneuver, safer braking on hill descents, better driver reaction time, and less stress on drivetrain components. Not to mention improved fuel efficiency and less tire wear.
Your truck is most probably very good when properly set up towing these Airstreams. Similar trucks have routinely towed similar Airstreams all over North America safely, and continue to do so.
Doug and Cheryl
2012 FC RB, Michelin 16, ProPride 1400
2016 Ram 1500 Laramie Crew Cab 4X4 Ecodiesel 3.92 axles
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