Max tow capacity and payload are based on overall ratings of the vehicle's frame suspension, wheel base, power train, drive train, wheels, brakes, tires, and hitch. That rating is also considering the driver is of average weight (about 150 lbs), and has no passengers or cargo. Upgrading one or two categories, opens you up to overloading on the others, and does nothing to increase the overall rating. Your vehicle has multiple ratings that are inter-related.
GVWR -- Max weight rating on the vehicle as it's going down the road.
GCVWR -- Max weight rating of tow vehicle and trailer (combined) as they are going down the road.
Max tow rating -- Max weight the vehicle is rated to tow, with a 150 lb driver, who has no passengers or cargo.
Max payload -- The difference between GVWR and what the vehicle actually weighed, when it left the factory.
Hitch rating -- What the hitch is rated to carry, with or without a weight distributing hitch.
Example:
Payload weight - increases the gross weight and reduces max tow capacity, pound for pound. If your vehicle is rated to pull 6200 lbs and you put 500 lbs of people and cargo in the vehicle, it's max tow is reduced to 5700 lbs and it is 500 lbs closer to it's GVWR.
Payload is used up by weight of everything and everybody you put in or on the vehicle, including any aftermarket accessories, the weight distributing hitch, and trailer tongue weight.
Another thing to consider, may be tire ratings. Your Sequoia has passenger rated tires. They are built for passenger comfort and have softer sidewalls, than those with "LT" (light truck rating). Cross winds on a long trailer, creates a lot of sideways push and pull on the tow vehicle. Soft sidewalls will flex side to side, more so than an "LT" tire. If the sidewalls are soft enough, and the trailer is long and heavy enough, this could cause trailer sway issues.
Check out this calculator (
Link). It may give you a better picture of what your options are.
Estimating tongue / hitch weight:
Average camping load (battery, propane, pots and pans, dishes, bedding, camping gear, water, and groceries, will add approximately 1000 lbs to the trailer's unloaded weight.
Average tongue weight is about 12.5 percent of loaded trailer weight.
Average WD hitch weight is about 90 lbs.
