It's working out when they changed them. They early E, F, J from what I can tell had the smaller beam windows. Likely because they didn't have the beam gun positions. It makes sense for them to have been made slightly larger on the P-2 and early Hs when beam armament was installed at the factory so as give the gunners a larger view around the aircraft. Whether all aircraft of the same variant all had the larger windows or if it was a gradual adoption with different factories incorporating them at different stages I have not had enough time to investigate yet, but I can confirm that your not going blind.
