The logic of PM=Oswald is plausible only if Oswald was selected post event as the most likely suspect due to Tippit shot and Oswald confronting McDonald in the Texas theater.
The MC rifle would have had to be planted on the 6th floor of TSBD within about 50 minutes post shots presuming that Boone and Weitzman did actually find the rifle at 1:20 pm.
However Tom Aleya suggests a different later time for the MC rifle being found when he filmed it being lifted by Will Fritz. Aleya also saw Fritz pick up the 3 shells before they were photographed and put them in his pocket. Fritz came back later and put the 3 shells back on the floor to be photographed.
So the alternate scenario here is that a conspirator shooter used a different rifle ( probably semi auto) and left 3 shells that were not MC shells. This shooter took his rifle with him and escaped out of TSBD ether unseen or mistaken as a plainclothes officer coming down the stairs as Luke Mooney went up.
Oswald’s account then of going “out front” and he having selected out all the employees he could have selected, Jarman and Norman , would suggest that Oswald was sitting in the Domino room 1st floor at approx 12:23. He saw J/N returning thru the back loading dock door, Oswald then went to the front entrance lobby at 12:25 and he was looking thru the glass wall when he was seen by Carolyn Arnold looking back at the TSBD.
Thus it is plausible that at 12:29 Oswald opened the front door INWARD , so that he could have exited onto the front entrance landing without disturbing any of the others standing out there. He could have easily slipped over to that west corner where he was be seen in the Darnell film raising some object up to mouth level. That object would be a Dr. Pepper bottle with a white oval logo on it. He then left that bottle by that.step where he had been standing one step lower than the top landing Thus lowering him to appear to be only 5’-2” in height relative to BW Frazier.
Because the current version of Darnell film has the PM figure with a white ring around the neck, the whole PM theory has been summarily dismissed so it would seem.
So despite some logical reasons why the PM figure could be Oswald if it’s a post event framing job, until someone can prove the white ring was added to the latest version of Darnell, there is not hope for the PM=Oswald scenario to be proved.