You can cut down a little more on the dust/dirt with some foam. Get strips of foam (the seat cushion type) and squeeze it in between the inner and outer fender all the way around the hole the passenger portion of the seat sits. You could probably use expansion foam if you're careful enough.
Retired USAF, IYAAYAS!
2008 V-Star 1100 Custom Bobber project
2011 Crimson XR with Forged Highway Bars / Hard Bags / Passenger Backrest, Ness parts including Smooth Layback Plate Frame/Mount / Rad 3 Mirror / deep cut grips / drivers floorboards /shifter peg / brake peg / passenger pegs. Witchdoctor black rack, Lloydz filter / timing wheel / VFC III, 7Jurock windshield, Drag Specialties seat.