This below is Z-248.

There is likely a consensus that JFK has been struck at this point. JFK appears to be reacting to something, that appears to be a painful blow.
Gov. JBC is a different story. By JBC's account, he is beginning to turn around to see what has happened to JFK. JBC has heard a gunshot, which he says he recognized as a rifle shot.
In Z-248, JBC is holding in his right hand his Stetson hat. JBC's wrist appears uninjured. This is an image of what happened to JBC's radius bone:

There is a large hole in JBC's radius, where a slug smashed through, passing from the dorsal to the ventral side, in the wrist-adjacent part of his arm.
This is what Gov. JBC told the HSCA:
Connally: I was knocked over, just doubled over by the force of the bullet. It went in my back and came out my chest about 2 inches below and the left of my right nipple. The force of the bullet drove my body over almost double and when I looked, immediately I could see I was just drenched with blood. (1 HSCA 42)Obviously, in Z-248, JBC is not doubled over. JBC is holding his Stetson, in what appears to be an uninjured wrist.
I have reasonable doubts about the SBT-LNT. The SBT-LNT are theories, and Arlen Specter developed the SBT working on the premise that there was a lone gunsel, who fired three times, and one shot missed. If one adheres to those premises, the SBT is the result.
Caveat emptor, and draw your own conclusions.