I'm pulling 6,500 lbs. with my Tundra and it's a great combination. I think as you hit the 7,500 lb. mark or so, you'll be OK on the flatlands but major mountains will show that you are at the upper limit. Make sure that you have LT tires on the truck, not P rated tires. I know that from experience! P tires will flex too much. Go with a good WD hitch and as advised by others, don't put too much weight in the truck bed. As you acquire gear that will be stored in the trailer, go for lighter weight products as it doesn't take long to add quite a bit of weight. As a rule, I never travel with more than about one third of a tank of fresh water and the black and gray tanks are empty.
I towed our old Sunline a few times with our Tundra. It weighed somewhere in the 7,500 lb. range and then we traded it in for our Winnebago. Reducing the weight by a thousand pounds or so was quite noticeable, especially in the hills of Ohio. If you plan to do a lot of traveling, especially in the mountains, you may want to consider a lighter trailer. We went out west last summer, and our Tundra/Winnebago combination handled the Rockies very well.
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