Currently doing something similar - 2011 F150 EB with Max Tow, Open Range LT272RLS (35', 8k, 800lbs tongue, 10k GVWR, not a toy hauler).
Many here will say we're crazy for considering that but the #'s all fit within Ford's guidelines. We have one of the better hitches (Equalizer with 14k bars) and on the maiden voyage it did well on the highway and back roads. Kept it at 65 or under, and even getting passed by semi's it didn't sway much. Had a "panic stop" when getting on the turnpike a tanker decided to cut in front of us. No Drama. Towed it to storage and it was windy (flags were blowing) and no sway other than the usual you get.
We do "feel it back there" but for me that's good as it reminds me I'm piloting 15k down the highways.
We definitely will be keeping an eye on it and if conditions warrant an upgrade to an F250 or F350 is an option. For now it tows fine as is and the only thing I'm thinking about is airbags to take some of the bounciness out.
But, you will be over just about every rating on the F150 so I'd think about either a bigger truck or smaller trailer.
