The hot shoe of the OM-1N will synchronize for electronic flash and the setting of the PC socket switch make no difference. The FP setting of the PC socket switch includes a short built-in delay to allow the Focal Plane flashbulb to "ignite". You could try some experiments with the flash mounted in the hot shoe. I believe that the Olympus system (Super FP mode of the F280) is set up that the flash starts firing as soon as the first curtain starts moving. I also think that the OM-1 is synchronized to fire the flash when the first curtain is fully open.