Hello,
Actually I haven't done.
But do know, if you fall under STEM program
You can have 17 month opt extension.
You need to file opt again for extension before your OPT expires
Also, if you file the OPT card and don't receive the card.
You can still continue working,
I am not quite sure regarding 180 days.
Also, if you have file for H1 and your opt expires, you will automatic get extension for that period
This might be the case for 180 days extension. Not sure.
I suggest to contact ISS office on campus
Hope this helps