If you are indeed correct -- that Billy Lovelady was still on the TSBD steps some 30 seconds after the final shot (while Officer Baker was apparently running past an interested Roy Truly towards the front entrance) and that William Shelley, having just intercepted Gloria Calvery (whom he knew well) at the "island" and then returned to the base of the steps where Calvery was now informing Lovelady that JFK had been shot -- then I suppose it suggests that Baker and Truly entered the TSBD within 40 seconds of the assassination.
What else would you like to add to this scenario?
Do you think Vicki Adams and/or Sandra Styles saw Billy Lovelady and/or William Shelley (or vice versa) on the first floor when they arrived there from the fourth floor?
If so, how long after the final shot do you think that was?
The Darnell footage shows Baker arriving at the bottom of the front steps of the TSBD building within seconds of the last shot. In an FBI report dated the 24th Pauline Sanders recalls seeing a police officer with a white helmet arriving at the steps within seconds of the shooting:
"Immediately after the Presidential parade passed she heard three loud blasts and she immediately realized that the shots or whatever it was came from the building above her. She said within a matter of ten seconds a uniform police officer in a white helmet ran into the building..."
Joe Molina testifies that he was stood directly outside the front door and saw Truly actually enter the TSBD building 20 -30 seconds after the shooting:
Mr. Ball: No, I mean when Truly went in; did you see Truly actually go into the building?
Mr. Molina: I saw him go in.
Mr. Ball: Where were you standing?
Mr. Molina: Right at the front door; right at the front door.
Mr. Ball: Outside the front door?
Mr. Molina: Yes, outside the front door I was standing; the door was right behind me.
Mr. Ball: Were you standing on the steps?
Mr. Molina: Yes, on the uppermost step.
Mr. Ball: You actually saw Truly go
Mr. Molina: Yeah.
Mr. Ball: You were still standing there?
Mr. Molina: Yes.
Mr. Ball: How long was it after you heard the shots?
Mr. Molina: Oh, I would venture to say maybe 20 or 30 seconds afterwards.Time trials conducted involving the movements of Truly and Baker had them entering the TSBD building within seconds of the shots. Along with these time trials we have the testimonies of Truly and Baker confirming this, the statement/testimony of Sanders and Molina confirming the arrival of these men within seconds and the Darnell footage itself showing Baker arriving at the foot of the front steps within seconds as Truly turns round as he, presumably, realizes Baker is entering his building.
All the available evidence points to Truly and Baker entering the TSBD building within seconds of the assassination.

This still from the Darnell footage shows the moment of Baker's imminent arrival at the foot of the front steps. On the west side of the steps Lovelady listens on as Gloria recounts what she saw.
If we could roll the footage on from this point we might see Baker arriving at the foot of the steps and making his way up the east side of the steps (I believe Sanders was stood on the east side). Truly, after turning around makes his way towards the steps and makes his way up them following Baker into the building. While this is happening Shelley is stood at the bottom of the steps and Lovelady is stood on the steps listening to Gloria.
Mr. Ball: By the time you left the steps had Mr. Truly entered the building?
Mr. Lovelady: As we left the steps I would say we were at least 15. maybe 25. steps away from the building. I looked back and I saw him and the policeman running into the building.
Mr. Ball: How many steps?
Mr. Lovelady: Twenty, 25.
Mr. Ball: Steps away and you looked back and saw him enter the building?
Mr. Lovelady: Yes.Mr. Ball: You went to the concrete between the two Elm Streets?
Mr. Shelley: Yes, where they split.
Mr. Ball: You went out there and then what did you do?
Mr. Shelley: Well, officers started running down to the railroad yards and Billy and I walked down that way.
Mr. Ball: How did you get down that way; what course did you take?
Mr. Shelley: We walked down the middle of the little street.
Mr. Ball: The dead-end street?
Mr. Shelley: Yes.
Mr. Ball: Did you see Truly, Mr. Truly and an officer go into the building?
Mr. Shelley: Yeah, we saw them right at the front of the building while we were on the island.
Mr. Ball: While you were out there before you walked to the railroad yards?
Mr. Shelley: Yes.It is this part of the testimonies of Shelley and Lovelady that seemed to support the Dunkel ID of the men on the Elm Street extension. Lovelady testified that they had walked about 25 along the extension when he heard someone call out which made him turn to see Truly and Baker still outside the TSBD building. However, the footage shows that 'Lovelady' never turned around.
Shelley testifies that they were on the "island" (the concrete spur where the two Elms split) when he turns around and sees Baker and Truly still outside the TSBD building. However, the footage shows there wasn't enough time for Shelley and Lovelady to have gone to the island before heading along the extension.
If we accept my proposal, that Lovelady and Shelley are still at the steps when Baker arrives and enters the building, then we have to accept that both men are lying about moving away from the steps before turning around and seeing Truly and Baker still outside the building. Both men are individually telling the same lie - that they moved away from the steps before turning around to see Truly and Baker still outside the building. This is confirmed by another lie that both men individually tell the WC:
Mr. Ball: Do you have any idea how long it was from the time you heard those three sounds or three noises until you saw Truly and Baker going into the building?
Mr. Shelley: It would have to be 3 or 4 minutes I would say because this girl that ran back up there was down near where the car was when the President was hit.
Mr. Ball: She ran back up to the door and you had still remained standing there?
Mr. Shelley: Yes.Mr. Ball: You heard the shots. And how long after that was it before Gloria Calvary came up?
Mr. Lovelady: Oh, approximately 3 minutes, I would say.
Mr. Ball: Three minutes is a long time.
Both men individually tell the WC that it was at least 3 minutes before Gloria Calvery came up to the steps!
Both men have created the same false narrative - they hear the shots as they are stood on the front steps, 3 minutes after the shots Gloria Calvery comes up to the steps and tells them about the President being shot, both men decide to investigate and leave the steps, after leaving the steps they turn around and see Truly and Baker still stood outside the TSBD building.
In effect, both men have testified that at least three minutes after the assassination Truly and Baker are still outside the TSBD building!Both men tell two lies that are exactly the same - Gloria took at least three minutes to get to the steps and that they had left the steps and turned around to see Baker and Truly still outside the building.
I have studied this issue extensively in two threads - "The 3 Minute Lie" and "Vicki Adams: The Lost Interview".
I have concluded that Shelley and Lovelady lied about how long it took for Gloria to reach the steps.
They lied about turning around and seeing Baker and Truly still outside the building.
They lied about going along the Elm Street extension to the railroad yards.
They lied about hanging around there and re-entering the building through the little known west door.
Shelley and Truly were stood on the steps when the shots were fired.
After the shots Shelley made his way out to the concrete spur where he ran into an hysterical Gloria Calvery running the other way.
He followed Gloria back to the front steps where Lovelady was still standing.
Immediately after hearing about the President being shot in the head, both men make their way back into the building.
They pass Baker in the lobby and make their way towards the back of the first floor where they are seen by Vicki Adams as she and Sandra Styles race towards the north door leading onto the Houston Street dock.
Vicki calls out to them about the President but they say nothing.
Seconds later Truly and Baker arrive on the scene. In his WC testimony Baker recalls seeing two white men hanging around near the elevators who can only be Shelley and Lovelady.