As the war moves on you'll be patrolling more in IJN waters so the 1X TC for friendlies won't be much of a big deal.
You have no doubt missed it the the battle of the Coral Sea is early May 42.
Even after the area around the Salomon Islands stays active through most of 42. The Markassar Strait picks up a little later as does the Luzon Strait.
Java and Flores Seas also good in mid 42 to 43 late..
Try this link for WWII battles.
http://www.combinedfleet.com/battles
Magic