I know we're off topic, but it is interesting conversation none the less.
I've had exactly the opposite experience as Stang when towing next to ED trucks. Just about a month ago on the rolling hills of I90 in Montana, I had my cruise set at 62mph and was cruising along in 5th gear with cruise control on and no downshifting. Mind you...the truck was wound like a top at 1900rpm! An ED blew my doors off on a long uphill. He must have been going 75 or so. The uphill lasted about a half mile. Just before the top, I passed him without any change in my "loping" condition. On the next downhill, he blew past me again. This happened for about 10-15 miles.
This led me to believe that he was interested in going that fast, but couldn't maintain it on those hills. I, on the other hand, could have easily climbed to any speed I wanted on the same hills.
All the x's and o's and arguing what if's..... I'll stick with what I have.
BTW, I'm averaging 10.8 mpg with 20k miles of towing. I consider that a fair deal for the power on tap.
PS: Seeing hundreds of other people towing on this trip, I can't believe how most people tow. I saw many, many less capable rigs that must run with their foot on the floor. Seems many folks don't mind abusing their equipment.