Proper Gear for Towing up Hills

You'll learn in a trip or two. I keep mine in 3rd instead of drive, with tow haul on. It puts my engine at about 2400rpm at 60mph and that is just enough for me to carry the rolling hills without loosing speed. Any lower in rpm and I either loose ground or downshift, both of which I try to avoid.

Zeelet, can you explain the converter lockup and fuel mileage? I feel when it happens (seems to gain abou 200rpm) but I don't understand how it relates to efficiency? I thought it was saving me from having to downshift, which would be more costly.