BC,
I drive a '97 Mercury Tracer (a Ford Escort in disguise!) I have a Yakima rack on the top and the ODC 816 rides up there just fine. Lots of 70 mph freeway driving and never a problem (knock wood!) I just strap it down with a couple of those nylon cam-lock type straps. My mileage drops only slightly. I can feel it up there in the Eastern WA wind sometimes, but I manage to stay on the road.
Jeff
"If you don't loosen up that buckle on your heart and start to chuckle, your gonna die of boredom, Safety Joe" ~John Prine