The Rage brand Black Widow Roof Rack fits perfectly to the Yakima factory bars. I installed it in about 1 hour.
Cost $99.00
extension-(not shown-nor will it fit without customizing) $39.00
Fairing-$29.00

Unit comes with the brackets included, which line the rack up perfectly and solidly anchor it.

http://www.discount-trailers.com/roof_racks.htm