Might find this interesting, it seems that "Hard" is (more or less) "Normal", presuming "1" indicates realistic value.
As per the config.txt file:
[Difficulty Settings]
//Easy, Normal, Hard, Elite
PlayerHullPoints=3,1.5,1,0.75
EnemyHullPoints=0.75,1,1.125,1.25
PlayerNoiseModifier=0.75,0.9,1,1.1
EnemyNoiseModifier=1.3,1.1,1,0.9
PlayerTMARate=1.4,1.2,1,0.85
EnemyTMARate=0.85,1,1,1.2
CombatRepairTimeModifier=0.8,1,1.5,2
PlayerWeaponReloadTime=0.8,1,1.5,2
[Difficulty Settings Campaign]
StartPointsModifier=1.2,1,0.8,0.6
WinMissionModifier=1.2,1,0.75,0.5
FailMissionModifier=1.2,1,0.75,0.5
TonnageSunkModifier=1.2,1,0.75,0.5
TimeInPortModifier=0.8,1,1.2,1.5
RestockTimeModifier=0.8,1,2,3
RepairTimeModifier=0.8,1,2,3
RescueTimeModifier=0.8,1,2,3
NumberOfASW=2,3,4,5