I have an 05 5.9 quad and tow a 9000+ lb trailer through the Rockies. Never any sway on stock suspension and I've never felt the need for bags or a sway bar. You didn't say what sort of hitch you are running, so I'll go out on a limb and say that I suspect you need a better hitch with anti-sway.
I recall the days when I had a pop-up camper that was about 3500 lbs. Even with that lightweight trailer, I needed to crank down on the friction anti-sway device.
I assume you are talking about a slide in truck camper and if you are on SRW's there is little you can do because of the height involved. I hauled Big Foot campers for many years (4000 lbs) on 3500 SRW and as I got older I got smarter and bought 2007 3500 DRW 5.9. There is no comparison...NONE. Duallies are the only way to go and much safer too.
You could try hitting up a metalworking shop to fabricate one out of larger diameter steel and then paint it. Not sure of the cost, but could help out.
Also for your air bags, if you only have one valve for the fill of both, you could swap to having a valve for each. This will keep the air from moving from one bag to the other around turns and help out with sway....
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