here's an attempt to model a shot through Kennedy in the Z190s (Note: this is not a SBT demonstration!).
You have JFK as far right as possible. It is possible he was not that close to the right side of the car. So you have to allow for a possible range of positions that are consistent with his position in z193.
In z193 his right upper arm is extended to the right. His forearm covers most of his upper arm, which means that his elbow is right of his shoulder and not much forward. The shoulder appears to be inside the car, which is consistent with the elbow extending out to the right onto the top of the car. That would put his midline at least 10 inches from the edge of the car.
A 15 degree path from the neck exit wound over the ensuing 24.5 inches goes 6.5 inches farther left, putting the bullet 16.5 inches from the right side of the car beside JFK. On the scale drawing of the limo CE872, the middle of the jump seat is located 15 inches from the inside of the right side panel. This is consistent with the printed dimensions which show that the width of the back seat - the distance between the inside back seat panels - was 60 inches. So, that would mean the bullet passed about 1.5 inches left of the middle of the jump seat. With Connally turned as he was in z193, the bullet would have gone to the left of his spine even if his spine had been pressed against the seat back, which it wasn't. With Gov. Connally's spine somewhat forward of the seat back and his shoulders turned right as we see in z193, I suggest that was enough to miss his turned back entirely. It may have grazed the back of his jacket as it was tumbling.
Mason has the entire torso, including the waist, turned. But the waist area would be more or less untwisted.
It passed above the waist. The thigh wound was above the waist and the bullet was moving downward from JFK.
Mason needs that area out of the way so his bullet can get pass Connally and strike the thigh. He's also claiming fragment strikes to the "wall" in front of Connally and to the driver-side sun-visor. No such such damage (holes) was reported in those areas.
I am not "claiming" fragment strikes. We are dealing with CE399! I suggest that CE399 stuck in JBC's left thigh but all we know is that it fell out of his thigh at some point because it was found on his stretcher. So maybe it stayed in and fell out as he was placed onto the stretcher or removed from it. Maybe it struck the hard wood panel in front at a few feet per second and bounced back onto his lap. We really don't know what it did. But it was not a fragment and at slow speed there is no assurance that the bullet would make a mark. (As far as I know, the front panel was not tested for lead or copper residue).
There were fragment strikes to the windshield and windshield frame but these were not caused by CE399!
In my view, the best evidence is that this damage occurred on the second shot. That fits what James Tague said (that there was a shot after he was struck) and Greer who reported hearing a kind of concussion on the second shot, which is consistent with the damage to the windshield and frame. The best photos of the underside of the flipped-up left sunvisor were taken at Parkland before they put the roof on:
It is not a great photo of the detail on the surface but there are some unusual marks that are consistent with damage to the underside of the left visor. I have been unable to verify that the sunvisors were inspected for damage. It seems not outlandish to think that a spray of fragments that struck the windshield, frame and went over the windshield to strike the curb near James Tague also struck the visor. However, that remains to be verified.