I know exactly what you are going through with your TV/TT towing test. We have a 2006 4-Runner v6 Limited with a upgraded Draw-Tite hitch, and trans-cooler
added, pulling a 2011 Jacyco X18D. All of trips have been over relatively flat terrain with just a few hills along the way. Never had any problems with sway or control
during interstate travel. With cargo for two young boys and the wife its a challenge to keep the total weight safe, and that is what it all about, staying safe.
We are currently thinking about upgrading to a 2008-2010 Toyota Sequoia for towing but the wife loves her 4-runner