i too am sporting yakima crossbars. I have the Thule Universal Pull Top 92726. found that the pull out feature works great since i do not have to climb onto the X to load the boards.

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2011 X5 35d 123,000 miles sport space gray/oyster

2005 X5 3.0i sport package Style 211
157,500 miles

2005 Chevy Avalanche Z66 BFG T/A Offroads