Interestingly, this past trip I took was in my large box truck. As stated prior, I simply don't drive the box truck over 60 as is. 60 is a comfortable highway speed that many semi's run at, and frankly you're not always doing lane changes to pass either, which makes the drive easier. The difference between 60 and 65 mph, across the country adds up to small advantages in time, so if you're making money for your mileage so be it. For recreational purposes though, I don't see the need whatsoever. In my case, while my box truck is monetized, I drive slower because my trucks brakes just aren't fantastic, and the gas mileage is better at a slower speed.
For me, unlocking or having 6th is more about running 60 at 1850rpm vs running 70mph down the road. I want the gear for reduced wear and gas mileage.
On the high profile, blowing around deal, that's definitely a fact I got familiar with in my class a that I had. I went from PGH to Las Vegas for SEMA and decided to take my motorhome. I was approaching toward Vegas from the south and nearing the area of the Hoover Dam. The winds were very gusty and it was moving anything with large profiles all over the place. Here, as I turn the corner and approach this bridge, a sign says "High profile vehicles use the center lane to cross bridge"...something along those lines, then a flashing sign saying "High Crosswinds"...I was like...awww hell...lol. It was interesting I tell you that....but yeah, you have to learn to get comfortable letting them move around a bit beneath you, instead of fighting every twitch.
My old whore here: