Some time ago I saw a documentary (on BBC or Discovery can't recall) where they stated that a sub of that last version went somewhere in the neighbourhood of Ireland and back to Germany undetected. I believe they even said it one did some rescue work. It came too late for deployment in combat missions. I understood. I'm sure your references are more accurate. It did sink ships then. Good news
Is it more difficult to spot in SH3/GWX compared to the other types? I haven't progressed very in my campaign so far.
"The XXIII was so crammed internally that she only carried two torpedoes and those had to be loaded externally in harbour, thus they lacked the offensive punch of their larger sister, the XXI Elektro boat."
Not very effective anyway.