You cannot call “seatbacks” for any reason in an automobile governed by the Shotgun Rules. You mush fairly recall shotguns when the rules allow.
Explanation: A popular residential variation of the Shotgun ritual is to call “Seatback” when getting up from a prized seat on a couch to go grab an ice-cold beer or to drain a now-warm beer into the toilet. Unfortunately, Seatback Rules cannot be mixed with Shotgun Rules, and calling Seatback in an attempt to retain Shotgun privileges in a car has been adjudged to be unfair, and is, therefore, a banned practice.