You lot should see my Yakima bars attached to the stock roof rack
of my Toyota FJ cruiser, which is 6'4" high as it is. Now put those
up there, with kayak cradles, and add the kayaks and we're talking
tall. But I U-bolted a 48" cross-bar on the front with a Yakima
Air-dam...

http://www.fjcruiserforums.com/forums/attachments/interior-exterior-visual-tech/16225d1191526092-yakima-off-shelf-solution-img_0223.jpg

Surprisingly, the fuel mileage doesn't suffer much with that mess
up there. Since the FJ has all of the aerodynamics of a brick to
start with...