I tow a 2021 Boondock 320S with a 2018 4Runner. I keep it to 65 on the highway and get ~13-14 mpg. It will readily go 70 but expect the transmission to stay out of the lock-up OD mode more often and thus the rpms go up and the mpg will drop to the 12s. I feel its a very good match for a 320S. Hills and grades are fine, stability is good with no swaying at all and it has no feel of the tail wagging the dog. You didn't mention what type of T@B. If you have or are looking at a T@B 400, then its probably a different answer. I can't speak to that but I do tow a 3300 lb boat - its OK but its working more. I would be skeptical of a T@B 400 but I like a lot of safety margin.
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