2015 26RBPR premier ultral lite F-150 towing questions

I know this isn't what you want to hear but you need to go to the 3.5 Ecoboost motor. Have a 2011 F-150 Supercrew,6.5ft bed with the Max tow package.
I pull a 34ft TT weighing 9000lbs. Box of truck is loaded with gear.
Truck is rated to tow 11,200 lbs.
Have towed my rig all over the country, mountains and all.
Motor is exceptional, pulls like crazy. 90% of the 420 Ft/lbs.of torque are generated at 1750 rpm.
New F-150 is rated at 12,200 lbs. towing capacity.