I've been playing computer games and simulators since the TRS-80 came out in 1979, so 35 years worth. Not non-stop, obviously!
The problem with cheating is a balance - if you don't cheat at all most games get tedious and/or irritating. If you cheat too much they get boring. It's a very rare game that is programmed so perfectly that a little cheating doesn't make it more fun rather than less, but again it's tricky to get just the right balance.
Running out of fuel in SH4 is irritating, crossing the Pacific at 10 knots is tedious, so it's the best place to cheat - a LITTLE.
What I did was use Silent 3ditor to open the \Data\Submarine\NSS_Gato\NSS_Gato.sim file, edited the 11:unit_Submarine\Ranges\Surfaced to
miles=18000
knots=15
That gave me a little more range at standard speed instead of chugging along at 10 knots. Eventually I gave up on the whole Pearl Harbor thing and went Asiatic, then started playing with the mission editor to create new resupply bases so I never bothered to increase the Sargo range.
So if you want to cheat a LITTLE do the same with your favorite sub, add ballast fuel tanks and increase the range by 2000 or 3000 miles. Don't go overboard and increase to 50000 or something, if it's too much you might as well select unlimited fuel.