Harrys suggestions are all good, not sure about #10 though where that
came from.

My biggest concern would be how the rig handles at highway speed. If
it doesn't sway a lot then just take it easy and you should be ok.
A rig that wants to go out of control while towing is the worst thing
for you to worry about.
If you just plan on accelerating slow and not pushing hard uphills
the transmission will be fine. I tow a 24 foot boat with my F150, and
I really could use a bigger engine, but I've towed it many, many miles
and had no problem at all engine or transmission. I think it's because
I never push it hard.

John C.