MMM dust! well I put gorilla tape over all the drainage holes (three in the front of the bed, three in the compartment's above the wheel well) then I put some weather-striping around the the two compartments at the back of the bed and finally I put weather-stripping around the tailgate. This cut down on dust quite a lot but the weatherstripping around the tail gate needs some work. Keep in mind that weather stripping around the tail gate does make it a little harder to shut, but if it keeps the dust out its worth it. There is still a gap around the rear window that I need to figure something out, but I just have not had the need as of yet to remedy that. I will take some pics of my efforts to keep dust out and post em up!
Post up some pics of yours when you get it done. Seems like every time something like this gets duplicated someone makes some interesting improvements....