I talked to Corbin customer support and they were clueless. The guy just kept repeating the instructions about transferring the latch. Duh.
I also asked if the later model bikes had a different part number or seat pan. He said they did not; same for all years.
Anyway, I think I solved my problem. Greywolf, I found I did have to bend the left side helmet lock hook out of the way for it to sit flush and not rock.
Then I took out the bolts holding the coolant reservoir in place and dropped the bottle down one hole, so the previous top hole in the bottle bracket now mounts to the lower mounting bracket hole. I put some locktite on it and made sure everything cleared and didn't rub, and the seat slipped in place perfectly and latched securely.
Does anyone know if the Corbin guy was right, and the seat pans are still the same regardless of year? If they are the same, I may send them an email with some pics outlining the issue and maybe they can devise a more elegant solution.