Just to prove I don't have all the answers (as if I ever did) I have this question.
We all know that the IRT City Hall station is on a wide curve and the original IRT cars with their end doors had no major problems platforming those doors. When they added the center doors to those cars at first it would not be a problem because those doors had separate controls and could be left closed ay CH.
The question:
What did they do when they made the later Lo-V's and there were no separate door controls. How did they prevent the center doors from opening? Did they only use the cars with the separate door controls on the Lexington Av Local until 1945 when the station was closed?
End of question.
I am assuming that by the time the Lo-V World's Fair cars were placed on the mainline the CH station had already been closed so that there was no problem seeing as the door postions were different.