Hi Doolar have you tried just placing a German Naval Base from Land Menue of the SH3 Mission Editor then Placing a German suface ship or AI IXB Uboat from Sea and Sub Roster Geman in the SCR Leyer of your Campaign Map Milk Cows and Resuply Ships like U-469 U-487 Thor Widder Orion ect.
Thats how I did it when I wrote the Steel Sharks GWX SH3 Campaign
Having the Uboat loop round (Hiden Naval Base at -200Mtrs) at 1 knot
hope this helps Chief Doolar keep up the good work Sir