Assuming you're correct for a moment and the unusual seating position is sufficient to explain the bizarre locations of the seven bullet wounds, there is still the matter of timing. Kennedy can be seen grasping at his throat wound for several moments in the film while Connally's wrist is still unharmed. This is a problem because the same bullet is supposed to have caused both wounds (throat and wrist) in the single shooter theory.

Also, I'm curious where you found that explanation; I'd like to check it out. The source wouldn't happen to be the History Channel, would it? I remember seeing a lot of assassination documentaries on there.