Take this for what it is worth. I have a 2003 Yukon Xl, same drivetrain as yours. I tow a 2011 Keystone summerland 26' loaded somewhere around 6100 lbs. I have taken it on two trips, one to the beach and one to the mountains, to the beach was a breeze, to the mountians it ran hard. Moderate hills I set it on cruise control to run at 62, it would drop to second and run 4500 rpm up the hill. I never really felt like I was out of control. It just worked hard. Going up the mountain side was slow, but I am fine running 30-40 mph for 3 or 4 miles. I don't travel far with it, less than 300 miles either way. I run a dual cam setup. I am about 100 lbs under my GVWR.
That being said, I am probably going to upgrade to a 2500 or truck within the next couple years. I tow the camper to the mountains leave it there for 3 months and tow it back. So I run a little slower and try to go on light traffic times. We just go visit it in the mountains when we want. For right now it does what I want it to do.
There are other hard side trailers out there. Ours is 5680 lbs dry, 5900 lbs on a scale, has a huge slide out, I can fit a family of 6 in there with a dog crate and still have plenty of room, it has a queen bed and bunk.
I would not try to tow the originally posted trailer at all. Not because it weighs too much but because it is too long for your TV. I think my 26' is as big as I would go with my Yukon xl. It is all about what you want to do with it. BTW, my wife and I looked at a hybrid too and had the same concerns, and they were more expensive than the hard sided ones anyway.
