Biggest thing you're gonna have to worry about is the gas you're gonna burn doing it. Even doing the standard 60-80mph drive to the mountain with my old rack on (thule flat ski carrier and a fairing, no box) would knock my gas mileage from like 25mpg to like 20mpg with the rack on. Boxes are even worse, and the drag just increases the faster you go.......... so 100mph will suck harder thanan asian hooker at an orgy.
I don't even have my rack on this year, it's a hell of a lot cheaper, and you can honestly get creative and pack everything in the car. Especially if you have an SUV.