The Balao boat is not supposed to be available to patrol with at Brisbane until after July 1943. May 1943 at San Francisco for New Construction. In this regard (as well as others), the game completely ignores the Active dates of the boat, and "rewards" the player who has scored really high with a new boat. We put some assignments in at Brisbane and Pearl for if you do get an early boat, you at least will not CTD, but... There is no way we have found, and we have tried a multitude of things with FotRSU, and all have been for naught, other than to tell the players to save at the green line when coming back into bases, and do not take a new command, unless you know what it is - which the only way to know is to go ahead and accept it, hence the idea of the Save when inbound, so that you can roll back. Did you save prior to coming into Brisbane before you were assigned the Balao? If so, go back to that save, and then do NOT take the new command.
