Most of us come here to Learn. Just admit you have Changed your position as to the Primary Reason for the shadow. No big deal.
Perfectly happy to admit that, Mr Storing. All I care about here is getting to the truth, one way or the other!

For some time now I have believed that BLUE arrow is Mr Oswald (i.e. Prayer Man), YELLOW arrow Mr Shelley (just behind Mr Lovelady)----------------

I tried (harder perhaps than anyone!) to find a
credible counter-candidate for Prayer Man, but I got precisely nowhere. It's looking more and more to me like Prayer Man really is Mr Oswald.
The way I see it, Mr Oswald-------------after his visit to the second floor lunchroom--------------stays indoors on the first floor, keeping an eye out (through the glass front door) for the motorcade. Not being one for mingling or small talk, he waits until the latest possible moment to pop outside. He takes up his position over by the west wall of the entrance. He's holding his coke & sandwich/apple.
Just before the motorcade enters Dealey Plaza, i.e. just
before Mr Oswald steps outside, Ms Arnold spots him standing behind the glass door. She does not notice him after that.