Tow, something is wrong here. I know you haul a heavy camper, but this?
Mine is a positive story with the Rancho 9KXL's. I've blown through two complete cradle to grave issues of the R9K's in 17 years and 165K miles. I ran them on one with an empty bed and nine when the TC was on. Just tonight I ordered another pair as the 2nd pair (which were replaced by 4WPtz on warranty) dissolved after meeting the Soda and Salt from the Mojave Road trips. That was very corrosive stuff which also took out my complete exhaust system. Still, i'm not fond of the cheap twist dial for changing the rate. It's prone to sticking or not working. I've even snapped a few off (the reason I keep all the old dials) from passing brush or rocks underneath.
You may be a candidate for double shocks on the rear axle. This was an option on Dodge trucks when I talked to Summit Racing tonight.
The catch with shocks for a removable truck camper is the dual nature of the load. Almost all shocks are one dimensional, one rate, which only stablizes something in the middle.
I've successfully had double shocks on some off-road rigs in the past but nothing as heavy as our truck campers.
Let us know how this resolves.
jefe