I play with English text and I don't think I've ever added anything to the other files - only EnglishNames.cfg. I think if you add the extra entries to the file for the language you are using for text parts of the game, you should be fine.
Basically what you need to do is make a back up copy of the existing file, and then add the extra entries for MFM ships to the one that's going to be in your game folder. You can do this by making a copy and stashing it in a safe place, and then manually editing the one already in your game folder and saving your changes.
Or you can make a copy of the existing file, add the extra entries, and save that new file to the data\Sea folder of the MFM before enabling it. It will get added into the game along with everything else when you enable the mod. JSGME will make an automatic backup of the original file and restore it if/when you disable the mod in the future.
|