It's seemingly random. Last week, for the third preview, I was quite literally in the very front row orchestra (Row C) three seats in. Another person from Theatre Twitter who was there was in the fourth row orchestra.
I have a feeling as word of mouth picks up about the show and people crowd the rush more, the seats may become less available or desirable.
(I think I got in on the rush before it became well-known knowledge since I nailed it on the first try and haven't been able to get in since.)
Check out my eBay page for sales on Playbills!!
www.ebay.com/usr/missvirginiahamm