The single most compelling argument against a shot at Z275 is that it is only 36 frames before the headshot which was fired at or just before Z311. That is less than 2 seconds which is less than the minimum time of 2.4 seconds the FBI determined the Carcano could be fired accurately. It has been shown that the Carcano can be fired in less than 2 seconds between shots but that is without taking time to reacquire the target and take aim. Oswald could not have fired a shot at Z275 and followed it with a precise shot at Z311. Why would he have even attempted such a rapid fired shot? At a bare minimum, there would have been 44 frames between Oswald's shots and even that is a stretch. For the headshot, he took almost 5 seconds to reacquire his target, aim, and squeeze the trigger.
Andrew, you need to go back to the drawing board.