A woman covering that 150 feet in 25 Seconds immediately following the kill shot is a non-starter.
How so?
Calvery may even have met Shelley and/or Lovelady near the "island" about 15 seconds after the final shot and continued on her way to the steps when they started walking down Elm Street Extension towards the railway yard / parking lot.
You want to go into how you ID'd the back of that person at the base of the TSBD, but you are unable to place Calvery in that same position to begin with. You basically are putting the cart before the horse.
There are many reasons for believing Calvery was the big/tall gal in Zapruder and Betzner-3 (you do agree that the gal standing to the immediate left of John Templin in the Zapruder film is big and tall, don't you?).
Do you agree that the face of the woman I'm referring to in Betzner-3 resembles the face of Gloria Calvery (you can google her name if you have to)?
If you'll go to the so-called JFK Assassination Debate - Education Forum, you'll see that not only is the big/tall gal wearing a dark-colored blouse and a dark-colored headscarf and standing next to her dressed in all-white colleague, but that a strip of the big/tall gal's neutral-colored skirt is visible in Couch-Darnell, too.
I could go on and on, but that's enough for now.
Get back to me after you've done some "research" on the issue at the Ed Forum, or maybe even here.
-- Tom