I towed my large coleman popup trailer about 1000 miles during the summer. It wieghs in at 3500lbs dry and I had it packed up pretty well. I might add that I only had about 1000 miles at the most on it at the time, so it wasn't even broke in yet.
Up from Salt Lake via I80 over to Northern CO. Driving impressions:
* Up I80...pretty steep grade. Ran like dream. 65mph to 75mph........no probs.
* Through the twisty turns to Wyoming. Got to slow down quite a bit as the weight pushes you around pretty good.
* Flats through WY. Ran about 72mph the whole time...any faster and the trailer got squirely and started pushing me around.
* Downhill portions. No problems with trailer brakes as long as I kept the speed appropriate.
* Cruise control worked flawlessly loosing 3-4 mph at the most at the steepest of grades.
I would NOT tow anything this heavy without trailer brakes. When your trailer weighs as much as you do, it's going to push you around.......do the math.
Also, some type of anti-sway system is very important. In the flats through WY, the 1st time I got it up to 72+, it darn near took me off the road once it started rocking. Took delicate touch(small slow corrections) to get that baby under control. It was scary, but it was pulling so well up until then, I found myself creeping up to speed limit of 75.
Anyways.....that's my impressions at that weight. I've towed a couple of small trailers(flatbeds, 1000lbs at most) and I didn't even know it was back there most of time.
WWV