Bill Seiko;
When heading home, travel on the surface at night and in the early hours. Go under for most of the daylight hours at least until you are approx 500km away from the nearest Japanese territory. Once you are out of aircraft range you can usually stay on the surface for the remainder of the voyage.
As mentioned, if you get an air radar contact do not mess around.....dive!
Stay under for a while then come back up and continue on your merry way. There is a bit of "up and down" involved until you're clear of enemy range.
What I usually do is take my compass map tool and put 500 mile radius circles over key Japanese locations (i.e. Tokyo, Okinawa, Iwo Jima etc). I assume a 1000-mile round-trip range for the average aircraft and these circle zones show me on the map when/where I can expect regular air activity. So far it has proved to be pretty damn reliable in that once I pass into those marked areas that's when things get interesting. Conversely it has worked the opposite way too in that once I'm out of those marked areas I can breath a bit easier and stay on the surface longer. There's the odd time when an aircraft shows up outside the zone but it's rare (your zones will have to adjust as the war progresses). I freely admit it's a fairly rough "tripwire" but as I said it's been pretty damn accurate so far.
Hope this makes sense and helps a bit.
