Doorman's t-shirt was clearly v-shaped and not round, and you can see it similarly on Oswald. Only Oswald wore a t-shirt like that. There is NO CHANCE that Billy Lovelady wore such a t-shirt.
Lovelady didn't wear such a t-shirt even when he primped and pranced to pose as Doorman. That aspect of the costume completely sailed over his head. He didn't get the memo about it.
How did Oswald's t-shirt get that way? It certainly wasn't store-bought. His friend from the Marines Anthony Botelho, upon seeing the Altgens photo, recognized Oswald right away based on that t-shirt. He said that Oswald had the habit of tugging on his t-shirts, stretching the collars out of shape. And, Botelho put it in writing.
It is Oswald's t-shirt on Doorman, and therefore, it was Oswald in the doorway. Period.