car top box problems
 

I've got a 2007 Cooper with the dealer installed Mini roof racks, and my own Yakima car top box, the kind that is long enough for skis. The issue is that the box prevents the tailgate from opening all the way (I've got a spoiler), unless it's mounted WAY far forward -- impossibly far. I've looked at the photos of the Mini branded car-top box (made by Thule, I believe, and which appears to be almost identical dimensions to my Yakima), and in all the photos that show it mounted (on the same model that I have, with the same spoiler), it looks like it's going to have the same problem. The dealer says it will not, but I also get the impression they've never actually mounted one. My doubts are doubled because the Mini box is not even shown on the Miniusa website, although the other roof accessories are there for sale. Anyone have any experience or advice? thanks!