I also want to point out that there are more 'physical' tools than ever to help you with manual targeting. Head and shoulders above all though is Hitman's Kriegsmarine Whiz Wheel/IS-WAS. Here is what both sides look like:
The thread to download it so that you can print it out and assemble it is here:
http://www.subsim.com/radioroom/show...highlight=whiz
The front side is based on an actual Kriegsmarine torpedo calculator thingy, while the back side is a circular slide rule based on the American IS-WAS back side, modified and interpreted by Hitman to conform with the color scheme and general format of the front side.