Great report.
DW & I are fixing to head out on our annual 4500 mile trip with our 13' Eco F-150 4x4, screw, HD. Have been on 3 short shake down trips of bout 175-180 miles. All three went from 5500 ft to close to 8000 ft and back down. 1st trip (8% climb last 10 miles) 8.6 mpg going up & 9.8 coming home. 2nd & 3rd trips were identical (was a gradual climb but same elevation). 2nd trip mpg was 9.2 up & back home 10.6 & 3rd trip going up was 10.6 & coming home was 11.4. So as we're putting more miles on truck it's getting better mileage. :B Like you I run no faster than 65 with tow/haul on & lock out 6th & kick cruise of when we go up a semi major hill. Trailer axle weight is 7600 lbs. Truck pulls the TT effortlessly, no sway or porpoising. Please keep us up dated on your mileage.
Milo