[Front Runner]

One thing to keep in mind is that there are some serious differences between the real world globe and Silent Hunter 4 Flat Earth.
This affects the ability to accurately model speed as well as distance traveled as well as fuel usage.
For instance, on page 107 of Clay Blair JR "Silent Victory" there is a reference of USS Gudgeon making a 3,400 nautical mile trek to Bungo Suido from Pearl Harbor. That mileage is correct when using Great Circle navigation, but in Silent Hunter 4 that straight line (Rhumb line) distance is closer to 4,600 nm! In Silent Hunter 4, we have to travel nearly 25% more distance also using ~25% more fuel.
It took USS Gudgeon 21.5 days to reach empire waters as they departed on Dec. 11 and arrived on station in Bungo Suido on December 31, 1941. That comes out to an average speed of ~ 7 knots which includes time submerged within the 500 nm airbase zone.
In order for us to travel the ~ 4,600 nm in the same time, we would have to travel an average speed of ~ 9 knots, a 25% increase in speed and fuel usage.
It is extremely difficult to balance these disparities within the framework of the SH4.exe. I also like to play with real world numbers in game, but keep in mind, many compromises have to be made in order to make the game playable, a task that our many expert modders have to juggle with continuously.