For anyone that doesnt already own it I strongly suggest you try and get hold of a copy of 'the u-boat commander's handbook' ,either from Amazon or you may be lucky to still find online copies.This is basically an instruction manual compiled by the uboat commanders themselves.It covers how the u-boat should be used,and how to perform specific shots under specific conditions,and also covers many other important aspects of u-boat warfare.
I was lucky to get a copy imported from USA at the time as stocks in Britain were dwindling fast,and in my opinion is indispensible to both the uboat researcher or u-boat gamer.
http://www.amazon.co.uk/U-Boat-Comma...0&sr=8-2-fkmr0
HURRY WHILE STOCKS LAST!
For those that cant get a copy this link is for an online document taken from the book,and may not be complete like the book is.However,it looks like it covers at least most areas.
http://www.hnsa.org/doc/uboat/index.htm