Default Sub Config settings for GameUserSettings.ini file, you don't need to add the config if you are ok with these settings:

[UnlockBlackwoodSub]
SuperSubBaseWeight=2000
SuperSubBaseWeightMultiplier=4
SuperSubNumberOfCrew=5
BWSubBaseWeight=2000
BWSubBaseWeightMultiplier=4
BWSubNumberOfCrew=5

Vanilla Sub Settings, in case you want the sub to be like the vanilla sub:

[UnlockBlackwoodSub]
SuperSubBaseWeight=500
SuperSubBaseWeightMultiplier=2
SuperSubNumberOfCrew=3
BWSubBaseWeight=500
BWSubBaseWeightMultiplier=2
BWSubNumberOfCrew=3