If I'm going 65, I'm looking to slow down, not speed up. I wouldn't be passing anyone that was traveling at 65MPH. I have passed people going 50ish with no problem.
Edit: I didn't really answer your question.... I have never gone 80 with something in tow, heck I don't think I've done it with nothing in tow.... so I can't answer that question. I can say, however, that I would rather tow with my 3D than a V8 gasser any day. Most of it is probably due to the 8spd tranny, but, when I describe towing to others, i usually refer to the 3D as "no drama". With a gasser it always seemed to rev higher and hunt for gears more often, the 3D will downshift, but you can also back out just a bit and stay under 3K RPM. To me, that is huge... I can't stand hours of towing while listening to a V8 at high RPMs shifting up and down through the gears.