You can get some relief in the SubName.sim file, but an alteration in one area of the sim, affects nearly all other areas. Each of the "main" entries in the sim file has a "Parent Node" that links to the dat file for the SubName. You would mostly be working in the , unit_Submarine section of the SubName.sim file, editing sections that are named appropriately, but the figures are not associated with anything resembling real life, so tread carefully. The use of
Silent 3Ditor (S3D) is recommended, unless you're a brainiac that knows hex editing...
One of the main differences between the real subs and game's subs (besides there only being two engines and two motors) is that the real sub could order ahead full on the port engine, and reverse 1/3 on the starboard (or whatever settings they wanted), which helped them turn much tighter.