I have towed my 55 Willys behind my 24S several times. Granted, the Jeep it has no tongue weight, but weighs about 2800 lbs. If I head north, I have a 4 mile, 5% grade I have to deal with only minutes from my home. I've had no problems either driving up or down "the grade". I've not needed to "downshift" going down, and can keep it at about 55 mph ascending with little difficulty.
I have been pleasantly surprised by my fuel mileage while towing. I actually got better than normal fuel mileage my last trip towing the vehicle than when I wasn't! But then, I'm not towing my Jeep at 70 - 75 mph either -- like we can drive on the open freeways. It seems like my rpm is a better indicator of what my mileage will be than whether I'm towing or not!