Okay,
if you just want to play FotRSU, take everything in the SH4FOTRS folder and put it in the Silent Hunter 4 Gold Edition folder. Deactivate, then reactivate FotRSU and any other mods you have installed in JSGME, and I believe that FotRSU will work for you then.
If you want to play FotRSU and keep an unmodded version of the game, make a copy of the Silent Hunter 4 Gold Edition folder, rename the copy to something of your choosing and carry out all the above steps with the copy folder. Then open up MultiSH4 1.5.exe (this will be in the copy folder after you reactivate FotRSU) and create a new save folder with a 3-character name (‘FRS’ for example). This will keep your modded saves and your unmodded saves seperate.
Let me know what happens, if it doesn’t work I’ll see if I can figure out something else
