What I did was take a couple of pieces of 2X4 lumber the right length to span the roof of the vehicle, set them on the factory rack next to a cross bar, then cut them so they fit on the side rails. Next, fasten them to the cross bars with U-bolts. This makes a secure rack at a fraction of the price of an after-market rack (have you priced Yakima to Thule racks lately?).