While I'm all about seeking flat routes for a tow, I am also much about avoiding traffic congestion along the I-95 corridor between about Fredericksburg, VA and Boston, MA, where manhandling a half-ton pickup with such a large trailer could be a huge handful along the "Ho Chi Minh Trail". I did recently suggest that a traveler planning a tow trip consider using the I-95 corridor through northern NJ when the alternative was I-81 and I-84 through the Poconos in PA, but the Poconos are more demanding, in my opinion, than the heart of the Appalachians to the west, in WV.

Just back in May 2015 my sons and I did a speed run to Buffalo and back for a wedding. It was a round-trip from Raleigh, NC so it involved much of the route you've found is the most direct. We did use the US 19 shortcut from I-79 to I-77 and that avoids Charleston and its congestion, is some 40 miles shorter (approximately--don't recall for sure), and is 4-lane all the way with only a few developed areas with stoplights. We accessed I-77 near Mount Airy, NC so experienced essentially all of the route's traverse of the Appalachians.

While I-77/US 19/I-79 cannot be called flat, it's for the most part not too bad. Yes, there are some long grades from about Washington, PA for the rest of the way to the foot of the Blue Ridge at Mount Airy, and there are a small handful of really long ones, but all in all, it's just not too bad. Given the option of that route vs anything involving I-95 into VA and I-85 from Petersburg to Charlotte, I'd run the I-79/US 19/I-77 route hands down. I do agree that if frozen precip is in the forecast, all bets are off and I'd seek the lower-elevation options involving I-95/I-85. From the northwest side of Pittsburgh the rest of the way to Buffalo was very nice--rolling countryside up to Erie and pretty much flat to Buffalo (following the contours parallel to the lake). Practically no congestion from Pittsburgh north.

If you do go through with the US 19 shortcut, be advised of the presence of a world-class speed trap in Summersville, WV. Just be aware of the speed limit dropping to 50 mph on each end of town, observe it, and you're good. Summersville is a good food and fuel stopping point, anyway, with lots of options available on both the northbound and southbound sides.

Down this way, you'll want to avoid entering Charlotte on either I-77 or I-85 during morning rush hour, if at all possible.

Safe travels,

Foy