Truck ride with big toy hauler

We are towing a N39SV Carriage with 06 Dodge 3500 SRW 4x4 - with Firestone air bags and Rancho 9000 shocks. The air springs add reserve spring capacity to the rear, and allow the truck to be levelled up under load. The additional spring capacity will overcome the shock's damping ability until they are adjusted into the 7 to 9 range. If I tow with the rear shocks set at 1 like I have them when running around empty, the rear suspension will "double bounce" on shallow dips in the road surface (not desert wash dips) but the little ones. Setting the shocks up to 9 takes that away completely.