Weigh the truck and trailer ready to go and I'd bet you are over the GVWR on the Expy. I just bought a trailer that is about 6500lbs on a Cat Scale with minimum water in it and has 8000lb GVWR. With two adults, a 4yo boy and a 50lb dog we are within 150lbs of the GVWR and 100lbs over on rear axle weight. (2009 limited 4WD with HD towing and Equal-I-zer 10000lb hitch) The truck and trailer manufacturers use some pretty shady numbers for towing and weights when they publish them.
I have realized you can find whatever answer you are looking for on the internet, and maybe ignorance is bliss, but I don't feel great about my situation and there is no way in hell I'd recommend anyone to pull a bigger trailer. My combined weight was 13860lbs, and you'll be over 15,000lbs.