Thule 300 feet and load bars with the Thule "Moab" basket, worked sort of okay for the Rubicon last year, but with the constant side to side flip flopping as the truck made it's way along the trail, the basket would loosen on it's clamped friction fit and slide on the load bars.
Prior to that I had an old Motomaster cargo box strapped on, until the old weathered straps broke. I used the cargo box inside of the rack and ratchet strapped it on for the Rubicon, kept all the luggage dry and dust free.
The basket is currently removed as I have my RTT on the bars now. One day I hope to replace the Thule stuff with a nice solid proper roof rack, the stuff is too light duty for any decent 4x4ing really, but it does the job for now.