honestly, i thought 78 was going to be too hilly, but 80 was pretty bad....coming south on 81 from 80 is pretty easy, 75% of it is on a downgrade....worst part of the pull is going back north from 104 (exit for rausch) to about 107 (other exit for rausch), it is a very long and steep pull, lots of rigs in the right lane with flashers on...i did the same, about 45 mph with hazards on, cooking my trans isn't worth making it home 5 minutes faster
the trailer felt pretty stable, didn't get squirrely or shaky...i tried a few different variations of loading it down, i found the best is two traps parallel running around the lower control arms, two crossed in the rear around the axle, and two on the sides around the sliders keeping it steady side-to-side
next on the list is definitely a trans cooler, at the top of a few long ascents i was touching 205-210* on the engine temp....on a hot day with no load i run about there, fortunately it was cool out when i was pulling...had it been in the 90s, i would have been hesitant to pull very long without stopping for a few minutes to cool it off
i dont mind pulling again with the u-haul trailer, the only other gripe i have is about the hydraulic surge brake which doesn't do a whole lot on gentle braking, only on descents and harder stopping (exit ramps, etc.)....once i have a place to store one, i will be getting my own trailer with electric brakes
one other thing i noticed, trailering seems to have helped with the break-in of the trans, it definitely shifts smoother on hard acceleration now