As others have noted, the payload is the Achilles heel for the Sequoia (see my sig). Our TT is just over 6K loaded and ready to roll and the Sequoia handles it easily. Now, having said that......
What model is your Sequoia? What power options do you have? What wheel size do you have?
In my research prior to purchasing (in Feb. '09) our SR-5 I noted a couple of things. First, the 20 inch wheel option reduces your tow rating. Second, higher trim lines (Limited & Platinum) often come with power seats all the way around and power folding 3rd row seats. This also reduces your tow rating.
IMHO you need to take your Toyota to a scale and weigh it, then run your calculations again.
