Unfortunately the 07 Toyota FJ Cruiser roofrack crossbars are not compatible with the direct mount option for the
Thule 835XT Hull-a-Port kayak rack or the
Thule 883 Glide and Set kayak rack. You will first need to install the
Thule 450 CrossRoad car rack system or the
Thule 450R Rapid Crossroad car rack system to the FJ Cruiser siderails. You can then connect any of Thule Racks kayak carriers to either of these base rack system bars. The only difference between the 450 CrossRoad and the 450R Rapid Crossroad is the cross bar style. The 450 uses the classic square black Thule bars while the 450R uses the new elliptical aero shaped silver Rapid Aero bars.
Also, just an FYI,
Yakima Racks kayak racks will not mount to the 07 Toyota FJ Cruiser factory roof rack cross bars either. You would need to first install the
Yakima Lowrider car rack system to the FJ Cruiser side rails. The Yakima Lowrider works exactly the same way as Thule Racks 450 CrossRoad and 450R Rapid Crossroad systems.