After finally having trained my ships in preparation for 2-4 and having fit them with a more effective loadout, I finally beat 2-4, but I didn't manage to kill the last two Ru-class Battleships. My fleet did amazing damage all the way up until the boss, where there were no double attacks and scratch damage all around and my reward was yet another Kongou. I blew all my resources getting Mutsu leveled to Kai and everyone repaired. Also found out Kitakami was actually ready to Kai as well.