I put mine on last year. It came with a black bracket on the back of drivers seat (have pillion too). I removed that and replaced it with the one from the OEM seat (chrome). Fit much better after that.
That same type of black bracket was on the rear of pillion also and I replaced it with the one from original rear seat.
Come to find out now, that is what Corbin is recommending on their web sit. Wayne

Black 07 America, Bags, Corbin Seats, Shield, Datatool Alarm, Sissy & Carrier, Engine Guards and Cruise Pegs. AI Removed. Progressive 412HDs & Intiminators. Misc upgrades.