Regarding sign ups past the number - while I have no control or influence is how TStar would run it - I would assume that all people who sign up who don't make it will be put as reserves, or substitutes.
This seems like a better option to me than having a substitute thread, so if one well known PvP Eventer Forumer leaves the community publicly, everyone doesn't just check who the first guy who threw his name down there is.
Plus, it adds more people to consider if any of you dirty rotten cheaters actually try to figure out who is on your team. Basically, it makes it even more difficult. Because we /don't/ want it done.
This event is probably doing to need some substitutes for safety, so I am assuming that a few more people could put their names down.
(Of course, acknowledging that they have read the well written Rules, Example Round and Example Battle Results)