I would put the beginning of Wiegman a bit later based on the Mark Tyler animation (Motorcade 63). Here is the first frame of Wiegman:
Mark Tyler's suggests that frame z280-81 corresponds to the position in which cars 11 (Cabell), 12 (Nat. Press) and 13 (Camera car 1) are at or very close to the positions shown at the beginning of Wiegman:
Thanks, that’s interesting. However it appears to me that, in his handbook, page 17, Mark Tyler explains that this is just a rough estimate. Here’s a quote:
4.3.3 Zapruder & Wiegman
Circa Z447 (see appendix E.11) is a very interesting point in the
animation as it
roughly synchronizes the Wiegman film with the
Zapruder film.
And this is from appendix E.11:
I believe that Dale Myers’ methodology is considerably more involved and exact. I certainly don’t remember all the details but he did document his methodology very well. Take a look for yourself if it interests you.