I think one of the hardest parts for a seat like this is doing the foam. Im still working on getting mine done. Ive got a roadliner myslef, seat looks allmost the same.
If you get one of the electric staplers, a nice strong one it will go thru and hold. Rivets also work very good and hold it very well with the plastic but be sure thats your final setup because once you rivet it its a pain in the butt to undo because the rivets spin when you do to drill them out.