If we're going to do wound and assassination-photo recreation, we need reasonably accurate models. Mine aren't there and may never be. I've hit a technology ceiling with my computer.
Meanwhile, soak it up with Cartoon Ernie and his Hum3D model. ( Link (https://www.jfkassassinationforum.com/thread/38/announcing-1st-deliverables-numbers-pledge) )
(https://farm2.staticflickr.com/1871/44708397612_98880c3a01_z.jpg)
(https://i.ibb.co/Yb3nD9J/nellie-seat-back-height.jpg)
The top of the jump-seat-back is several inches below Connally's armpit area and so did not interfere with the bullet path.
See where the top of Nellie's seat-back is in the above photo; it can be seen in the side-window of the parade bar. The Governor's seat-back is the same height.
(http://ss100x.com/LIMO1961.jpg) (https://stumptownblogger.typepad.com/.a/6a010536b86d36970c01b7c8b2a5aa970b-800wi)