[soloshrov]

Thanks for the response but ive played nearly all the way through 3 times so I was looking for a way to spice up early war, and I figured out how.

You have to go into the Flotilla mission file for the German campaign and edit each flotilla, all you need to do is composite whichever sub you want into the flotilla and add a mission set behind it. Example here

[Flotilla 4.UserPlayerUnitType 3]
ID= F4XXI
NameDisplayable= Type XXI U-boat
AvailabilityInterval= 1940-04-01, 1945-01-01
IDLinkUserPlayerUnitType= XXI
UnitTypeCommonality= 16
IDFlotillaLinkTransferTo= NULL

Then you add it into the careerstart file and boom, CTD fixed and submarine is playable at start, but you then fall into another issue. The game tries to give you objectives in Freemantle and the rest of Oceania, to fix this I simply went into the patrol files and set the Freemantle date to 1945 and boom, Atlantic convoy raiding Missions in the Type XXI or any sub in 1939.

If anyone finds this thread looking to do what i did but wants a proper explanation ill come back and explain everything.