Friday from 8-12pm, we are going to launch an OPTIONAL program in a designated area, where assistants, not authors, can allow readers to purchase unsigned books early. Anyone who does this can still sell during the event. In theory, if even 25% of the people who want to get to you, buy early, this should allow authors who have huge lines to move them faster, and to be able to spend the time in front of readers chatting, not performing a transaction. It would also allow you to sign more of their homemade items, which makes the readers so happy. This again, in theory, also allows readers to move through and see more authors. 

This should be the SAME readers you are already hoping to get to. I would not suggest bringing extra books. Yes, you could sell out Friday morning, though readers have exciting events to attend too so I think this is highly unlikely, but everyone would need to come to your table and get the books signed. Even if the readers buy from your pre-sale table they can still buy at your table, too, if they decide they want to buy more.