I did the return tow this weekend. Very similar - 895 miles in 16 driving hours over 2 days. Averaged 56 MPH but fuel consumption dropped 1 full MPG to 8 MPG. I think the return tow has more climbs, and we had a headwind coming out of Redding and into Oregon which sure didn't help. I also pulled some 425 miles with the gray water tank almost full.
I usually set cruise at 65, dropping to 60 or even 55 for the big climbs. I run in Tow/Haul mode, locking out 10 gear. The engine/trans worked wonderfully. Power was never an issue, and the trans was always in the right gear. Very little hunting. It'd kick down from 9 to 7, and then 6 or 5 on climbs, rarely going over 3500 RPM. On descents it would downshift as far as 4th and run at 4000 rpm. The engine braking was noticeable if not strong, and it helps. I have the brake controller set at 10, and on occasion I'd use the lever to apply trailer brakes to help me slow down.
I'm very happy with the HDPP setup. It towed beautifully, and I was for the most part relaxed for almost 1900 miles of towing. Weather was great, traffic light, not much wind, no rain/snow so that helped too. A few observations:
1) I think the front shocks are underdamped for the spring rate. The front pogos 2-3 times after a dip. I will replace them in the Spring with something better. I put Pro Comps on the rear and they feel good.
2) Power tow mirrors could go out 2" more. It'd be nice.
3) I miss the gauge showing fuel consumption over last 5 fill ups. Only option now is 30 minute chart.
4) When we did run into wind, I could feel the trailer moving a bit. It's a big sail back there. I think a better hitch and better front shocks will help. E rated tires might help too as the stockers are C.
5) Truck is quiet and comfortable even towing. No complaints from DW, 2 kids, or 3 dogs.
6) Not sure I need a tune. I had a 5Star tune on my 2011 EB, but this one makes plenty of power and tranny is spot on. I would like a little more responsiveness from the gas pedal though. It takes a really good push to get a kick down.
Looking forward to many more tow miles. Very happy with the decision to do the F150HD over the F250.
Mike