I had some fun a few days ago. I wanted to look at some trailers at a dealership and went in there as if I knew absolutely nothing about towing and trailers (not far from the truth actually!).
Anyway, the dealer asked me what truck I had and looked up the max towing weight, which is 9180 for my truck. He didn't ask any other questions about the truck such as what my payload was listed at, what and who would be in the truck, would I be boondocking, or anything else. Every trailer he showed me was about 26-28 feet, which is much longer than the 20-23 feet I suggested I was interested in. One that was actually very nice, was a 27 foot unit with one slide and a dry weight of 5600 lbs. GVW was about 7400 lbs. I guess I could pull it with my truck, but I wouldn't be comfortable with it. Of course, he said it would be no problem at all.