Choose as home base "Pearl Harbor" in the PACG generator when creating a campaign. Since Pearl is right of SH2 map's end (Which lies exactly in the offical daytime division area) and you can't sail there, I decided to use it as an easy option for those who wish to start in the patrol area already. You will start there and the fuel you have will be just the one left after having eliminated the amount needed to travel from and back to the base. So when you run out of fuel or torpedoes you hit ESC and the mission is correctly finished, no need to return to base
Happy hunting