Man, I hate blowing up a post... had most of a reply done, and did something and ended up back at the site's menu, and no amount of "Back" did anything to get my post back... ouch... heavily edited version follows:
When doing edits along these lines, it's best to make a JSGME compatible mod that can be easily removed if some screws up. Make yourself a working directory, and I'll say that you name it "MyModExperiments". Below that, make another folder, and we'll call it "MyCrewFixMod". Below that folder, make a "Data" folder. Below it, make a "Submarine" folder. Go over into the mod you downloaded, and copy all the submarine folders under the Submarine folder there, and then paste those into your Submarine folder. Opening a 2nd Explorer window is the easiest. Each of those submarine folders has a like-named UPC file in them. The files in the folders that you just created are the ones you'll do the editing to. That way, your game files stay the same, and the mod files stay the same... If you really get into it, check out the files in the "Game Folder \ Data \ UPCData \ UPCCrewData" at some of those files... Just be sure that you back everything up!...
When you get finished with your edits, put the "MyCrewFixMod" folder into the MODS folder of your game, and use JSGME to enable it. See how you did. Something blows up on you? Exit and use JSGME to disable the mod, and then try to find your mistake(s). You can use WinMerge to help you with reconciling the downloaded mod's Sub UPC files with the TMO / RSRDC versions...