I do not actually go after the carriers, I just want them to move closer to Japan like you indicated that you did. I build a mix of fighters and bombers, plus an AA gun and some units on Hawaii. Generally, I use the bombers to hit anything near Rabaul, and the fighters to beef up other islands. As I said, I go after the carrier concentration with subs, and only attack the carriers after they either split up or I have sunk one or more. With respect to attacking in several directions, that is what the Japanese did historically, but I figure that they have to go after either New South Wales or India in the end, and reinforce them as I can. I still concentrate on taking out the transports as that makes invading Australia pretty difficult, and I can concentrate on defending India. To win the game, the Japanese have to attack and take those two areas, and with new production appearing only in Japan, no transports makes that hard to do as well.