Thanks for your thoughts. As far as trailer weight goes, I weighed a mostly-equipped trailer in Houston, Texas to the tune of 8800 lbs., with some fluid in the tanks. I picked up the last of my gear in Dallas and haven't weighed it since, but we're talking about some kitchen utensils and t-shirts. If I'm at 9000 I'd be surprised. To be sure, I took it to a truck stop in Denver after coming down the mountain, but the scale was closed and I didn't pursue it further. Regardless, I'm towing less than 75% of the printed maximum capacities, so I expected better performance.
Just got back from the dealership in Denver where I was essentially told that I shouldn't expect to be able to tow even 9,000 above about 35 mph in those conditions, and that I should have bought the diesel if I expected better performance. Not shocking news. I went in to buy the diesel and was convinced of the power of the 6.4L HEMI as its equivalent or better. Obviously a bad choice on my part, but I asked all the right questions and was just given bad information. I even took the specific weight information for my RV to the RAM dealership to confirm weight compatibility, since I wouldn't have a chance to test drive the truck with my unit in tow. I was assured the new HEMI would perform as well as the Cummins.
You can say whatever you want about it or whatever else makes this my fault, but I only posted because the initial thread of this conversation was about the pros and cons of the 6.4L HEMI, so I thought I'd share my experience. I have tested the trailer brakes, and they're fine. I have had full diagnostics run on the truck by two separate dealerships in connection with the busted fan clutch I got at about mile 3,500, and today I finally spoke with someone who has towed a fifth wheel behind the Cummins and the HEMI and honestly told me what to expect with the inferior engine.