If said rig is a high enough gvwr to not meet cafe studs, all you drive is 60-65 mph, why not axial yourself to high gear to towing at max weight you will be. Allow to USD a deep low, assuming you pull grades steeper than 12% as current min tow rating specs are,and have a.better tow rig for MY application, not some person that thinks they know what I need. I rarely am in an area I can drive over 60 mph. And with in my state, if over 10,000 gvwr, max speed is 60 mph. Don't see a reason for a great that will allow me to cruise at 80 mph.
Marty