With the new rules it seems to me that an airbase in Korea would be the way to go every game, stationing 3 fighters in Korea and at least 3 in Japan if theres any sense that an attack on any vessels or Japan itself is imminent. That would give you an extra 6 fighters to defend SZ6. Correct me if I’m wrong.
I did that in a game last week. Worked great. The U.K. attacked my Japanese fleet first and then a small ANZAC fleet did the same on their turn all in the same round. Wiped them all out with small losses.