You do realize you have the SBT happening as the JFK Limo approaches the Thornton Sign? This position would put the Limo at a point where it is just about straightened out after making the turn onto Elm St. This is close to where Croft were standing on the (S) side of Elm St. And your SBT Shot would be the 2nd shot by 1 shooter inna 3 shot scenario? At some point prior to this, the 1st shot was fired. And there needs to be the required time to work the carcano bolt action between the 1st shot and the SBT/2nd shot. So this means you Now have Shot #1 happening while the JFK Limo is still on Houston approaching the turn onto Elm St. And on top of all of that, you have Shots #1 and #2 being fired much closer together than shots #2 and #3. Really?
Just to update you: I don't have the SBT happening. There is too much evidence conflicting with it.
The second shot SBT is a non-starter as there are over 20 witnesses who recalled seeing JFK react to the first shot. Not a single witness said JFK continued to smile and wave after the first shot.
The evidence from many independent sources puts the first shot occurring when JFK was between the lamp post and the Thornton sign (*1). At that point, JFK was quite visible from the SN:

There is consistent evidence that each shot struck at least one of the men. The first struck JFK. The second struck JBC in the back (and JFK's hair on the right side flew up at the same time as the second shot, according to George Hickey) and a fragment struck the windshield and frame (Greer sensed a concussion indicating that something hard was struck) and another fragment went a bit higher and on to strike the curb near Tague and hit his cheek. What the third struck is not an issue.
All I am doing with the 3D model is seeing the trajectory from the SN of a bullet through JFK's neck. It appears that it could have caused JBC's thigh wound. He never did notice it. It is possible that CE399 bullet obliquely struck the thigh butt-first (as Dr. Gregory said) embedded a bit of lead in the femur and then hit something in the car causing it to bounce on JBCs clothing or, possibly, as Landis is now saying, bounced backward off the partition or bar in front of JBC and then into the back seat.
(*1) e.g. the first shot being after z186 (Betzner) after z181 (VP car occupants) and z191 (VP Security car occupants), before z202 (Phil Willis), between z190 and z202 (Linda Willis based on alignment of JFK and Stemmons sign from her position); Mary Woodward (just after the President passed by where she was standing); witnesses along Elm St. such as Billie Clay and Georgia Hendrix (a few seconds after the president's car passed where they were standing), Gloria Calvary, Karen Westbrook and Carol Reed (the limo was almost directly in front when the first shot occurred).