How to add Project RV Interior mid-save

This method works for single-player. I haven't tested it for multiplayer, but I imagine it should work.

1. Start a new game (save) with all mods you have now + [B42]Project RV Interior
2. Once it loads, exit the game. Rename both saved games to "NewMapSave" and "MyMainSave".
3. Go to your save folder in C:\Users\YourUser\Zomboid\Saves\Sandbox
4. BACKUP YOUR "MainSave" FOLDER - just in case
5. Copy and overwrite the following files from that "NewMapSave" folder to your "MainSave":
   map.bin; map_t.bin; map_ver.bin; map_worldgen.bin; metadata.bin.
6. Inside your "MainSave" folder, go to the folders: "apop", "chunkdata" and "metagrid"; and delete all files that end with the following coordinates:

87_46
87_47
87_48
87_49
88_46
88_47
88_48
88_49
89_46
89_47
89_48
89_49
90_46
90_47
90_48
90_49
91_46
91_47
91_48
91_49
92_46
92_47
92_48
92_49
93_46
93_47
93_48
93_49
94_46
94_47
94_48
94_49
95_46
95_47
95_48
95_49
96_46
96_47
96_48
96_49
97_46
97_47
97_48
97_49

7. Inside your "MainSave" folder, go to the "map" folder and delete all folders whose number is 2805 or higher.
8. You're finished. You can log into your game and check if it worked.