Had an ARB canopy on my last Ute - found that leaving the sliding window at the front of the canopy open was heaps more effective than the vent in keeping dust out. Tub wasn't sealed, did the Gibb, Oodnadatta Tack, Mereenie Loop, Dalhousie, Old Ghan track, Painted Destert, Jim Jim ect........... no real dust problem to speak of.
The canopy wasn't up to that many corrugations though, but that's another story!