My dually actually rides best at 12 psi. A buddy's F250 rides great at 20. His other truck rides best at 5 psi. Do a little playing with it. You may actually like 3-5 psi best. When loaded, play with it too. It may take a while to try the different settings, I would try them in 5 pound increments until you get it right. That is the main reason I went with an onboard compressor so I could adjust on the fly. I found this out after towing down a couple of different interstates with changing road conditions. Now, I can change the pressure as the road conditions change.
2012 Sandpiper 365SAQ weighing @ 15k, Onan, 2nd air, slide toppers, TST
2013 F350 6.7L Lariat 4x4 CC DRW,Viair 1007, Ride-Rites, Edge CTS, B&W
2001 Chevy 3500CC DRW 4x4, 8.1L, 4.10 gears w/ Detroit TrueTrac
2001 Ford Excursion Limited 4x4 7.3L,V/B Spring Mod, ProComps, Hellwig Swaybar, & other 'Necessities'