Tips on towing over 6000lbs with my 1st gen?

Going camping in middle of July and my parents are wanting me to pull a 31' Sportsmen that weighs #5785 dry. I'm estimating with all my wife and I's gear plus the camper combined around 6500lbs. I have factory towing and 7 pin and all that jazz but I'm looking on inputs on what everybody else is pulling and how it handles in their first gens. I drive a semi for work so I'm no stranger to pulling but never pulled anything besides a small enclosed with the truck so I'm interested in feedback and tips and advice

 

Get a brake controller if you don't have one, Toyota recommends no more then 3500lbs without the use of aux brakes. Weight distribution hitch would help a lot with a trailer that size.

5klbs in Colorado is slow going, so I would expect to be slow.

I tow a 18' travel trailer. The base weight is right around 3500lbs (they don't include options when they list weight :A/C, microwave, larger fridge so keep that in mind). When loaded with water and all supplies it is just over 5klbs. Weight savings can be had if you don't fill up with water until you get to camp, I can't because I almost always do dispersed camping.