Thanks Jeff - we thought there must be something behind that center plate but didn't want to pull to hard. - Installed the BMC this morning. Car is breathing better - gotta love the Italian design !! but it gave me an opportunity to tinker !The Backrest portion of the rear seats unbolt by removing the cover plate that is behind the fold down center armrest. You just need to pull on it ( more than you may think ).
Then you can access the screws to remove the top rear deck as they are just under the speakers.
Hope that helps