@hitmand and alex
Yes I am aware that the type never became operational

however, many types never did, was any of you for example aware that an upgrade of the IXD2 was planned as well? The type IXD/42, almost similar apart from engine layout, it was to have had a more powerful diesel engine and electric motors allowing an underwater topspeed of 7.6 or was it 7.9 knots, but it never became operational either, one was finished however! But never put into action as it was in 1945. Many types were laid down, a few even finished, but never went to combat, they are all relevant and interesting though I think, and since we are not talking about putting a walter boat or a nuclear cruiser missile sub into the game, but boats that were actually constructed I cannot see that it should be unrealistic either.
In my eyes I have bought a submarine simulation, I know it belongs to a certain era yes, but it is however a subsim, simulating tactical and technical aspects of submarine warfare at a given period in world history, not a history book, I know what happened to the unterseebootwaffe and not a das boot simulator either