The U-Boat Missions Add-On in SH4 Stock is lame, to put it politely... All they did was basically take the files out of the US Pacific side, and put them in a "CampaignGE / CampaignData folder and change a few names to protect the guilty. You will eventually get assignments to the Indian Ocean, but the set-up for the whole thing is rather thin. In FotRSU, all we did was make the ship calls compliant with the FotRSU paradigm, but all else is basically stock. If you really want to do the U-Boats, then you need to do Fifi's re-working of the OM / OMEGU mod combination with his "
Dark Waters" mod, or the original OpMonsun from lurker_hlb3. Either way with those mods though, they will interfere with things on the US side, and will require their own copy of the game and separate Save folder - Other than you can (more or less) do TMO with RSRDC and OpMonsun in the same game folder and Save folder, though you definitely have to follow lurker's instructions to the letter at
[REL] Operation Monsun. It can be great fun, if you don't mind "dying" in about 2/3 of your "starts"... lol
btw, you can cause more of the US convoy and / or Merchant ships to "announce" themselves by editing the lines "ReportPosMin=" and "ReportPosProbability=" in the mis files for a given "layer" file. As it stands, folks had complained about the frequency of the same in "regular" SH4, so it seems that the percentage of reports was turned "down" in the UBoat Missions...