Itek said 6.4 +/- 2.2 inches. But that was also based on stereo viewing Z frames 183 and 188. Nobody posits a shot at that time.
I was going by memory. But at in the footnote 6HSCA49 they quote Itek as saying that JBC was 10.2 to 20.3 cm inboard of JFK. The would be 4 to 8 inches or 6” ± 2”.
I don’t think it matters too much which frames prior to z195 one uses because neither appear to change the position of their midline prior to that point. I see a noticeable difference in the position of JFK between z193 and z225.