Not sure what to think about the "one boat per challenger" rule, I think this is a big disadvantage to the challengers.
Traditionally the first boat is always the one where new ideas get tested, whereas the 2nd one is the actual match boat.
With this rule there is a risk that they will "butcher" their boats to incorporate new design ideas which could impact the structure and possibly safety.
Both Oracle and Artemis destroyed their first boat so not having a 2nd one would really be an issue when anything catastrophic happens.