We have your same truck, and have a 2010 Keystone Cougar 324rlb, and have been enjoying it since we got it new. GVWR on the unit is 11.9K, and the truck tows it very nicely up and down the long heavy hills in California, Utah and Colorado. This unit has a separate rear room with slide-out, a queen sofa bed and loft in that rear room, and its own half bath. Our youngest kids and grandkids really enjoy that room. Our kids appreciate the privacy of their own room and bed, and the grandkids love the big loft area.
This unit has a light pin weight of 1800-2000 lbs loaded. We are well below the truck's "unofficial" RAWR with after market 285/75R16 tires rated at 3750 lbs each (effectively setting the RAWR at 7500lbs), so I don't sweat that and the truck handles the unit very well and comfortably.
Good luck.