I tow a 13 Explorer with a kayak on the roof as well as up to 4 bikes on the back. I’ve towed this out to CO up in the mountains with no issues. The Explorer is pushing 5k lbs loaded like that.
Don’t be afraid to let the V-10 rev, it needs the RPM to keep moving. 4000-4500 rpm is normal in second gear going up a mountain at 45-50mph! Loaded I’m right at 24k lbs. make sure you always have a tow Haul engaged.
I have since installed a tune from 5star. I haven’t been in the mountains with it, but it does make a difference.