Board Thread:Questions and Answers/@comment-182.20.165.142-20150317075536/@comment-25477086-20150317185055

Unfortunately for the 6 ship version of this quest, you have no control over any of the branching. It will just have to come down to compass luck to get sent to the boss.

Now in the event you clear the 6 ship version but not the 4 ship version (S rank required), you can mix in other ships like an AV which has a higher chance to lead you to the boss node.