If i still have the mission dates correct (ill have to doublecheck on that), in the career start.cfg, change both the start dates for that start entry to 4th december 41. The game does things 1 day ahead. By setting the date to the 4th, you should start on the 5th, which means you'll leave for patrol on the 6th.
If that doesnt work:
i may have the mission dates off because i had to go back and edit things when i decided to scrap it. In the misisonobjectives.upc (i think thats the name
), at the very bottom you'll see two missions i added. Make sure they're available on the 5th of december. Failing that, change it to the 4th.
Then check the flotilla.upc for the boat type you want ot use, and make sure the first mission dates are correct. Should start on the 5th.
All said, it will probably work for you quite easily. Enjoy the jap flyover at 0730, december 7th, 1941. (didnt finish scripting things
)