I have the Atlantis 1600 and have driven thousands of miles at 85. The box is rock solid. All these warnings about crosswinds seem a bit silly to me. Sure your adding some height and surface area to the X, but I'd say it's still alot less than any of the minivans out there. The only way you will know the box is up there is when you get out of the car.

It's not just height and surface area, it's the weight of a fully laden roof box shifting the centre of gravity much higher = greater chance of tipping in cross winds. This risk is especially increased if you have to change lanes etc suddenly. We call it the 'elk test' in Europe and it's found a few normal cars can have serious issues when they have to swerve at speed especially if a high mounted load is also involved.