I incorporated GWX's radiolog into IrishRed's radiolog, been using IrishRed's since RUB.
Here's the sources he listed in his work, maybe they can help you out.
http://www.U-boat.net - where much of this info came from. (Plus the Uboat.net's featured "Conning tower"
http://www.uboatwaffe.net
http://www.uboatarchive.net - This website run by Jerry Mason has English translation of the BdU KTB, highly reccomend.
Books used:
Hitler's U-Boat War : The Hunters, 1939-1942 - Clay Blair
Hitler's U-Boat War: The Hunted, 1942-1945 - Clay Blair
U-Boat Operations of the Second World War, volume 2: U511 - UIT25 - Kenneth Wynn
U-Boat Operations of the Second World War, volume 1: U1 - U510 - Kenneth Wynn
U-Boat Command and the Battle of the Atlantic - Showell, Jak P. Mallman
U-Boats under the Swastika - Showell, Jak P. Mallman
Iron Coffins - Herbert A. Werner
Uboattwaffe, Marine - Kleinfampfverbaende 1939-1945 - Waldemar Trojca
The U-boat Wars - Edwin P. Hoyt
The Uboat War: The German Submarine service and the Battle of the Atlantic - David Westwood
Axis Submarine Sucesses of World War II - Jurgen Rohwer.
Memoirs: Ten years and Twenty days - Adm. Karl Doenitz
U-boat War in the Atlantic: 1939-1945 - H.M. Ministry of Defence (G. Hessler Ed.)
Business in Great Waters - John Terraine
The Battle of the Atlantic - Terry Hughes and John Costello
I know a lot of people complain about the radiolog messages but I find they help the immersion factor for me.
Good luck and looking forward to your mod.