http://www.subsim.com/radioroom/show...98&postcount=8
I have not played the German side for awhile. The link above will help you figure out how to set set the TDC for the German side. There is no position keeper for UBoats.
A good mod set up is in the ATO forum. It is OM/OMEGU/KIUB. Learning the UBoat side takes awhile.