The UI is partially defined in the database file; probably the database file that has been altered to make the game believe there are 6 players is not for v49. And the author included needless files.
Since it is a simple mod and it is basically part of what I did for my mod I can share a new version here: https://drive.google.com/open?id=1QojvO6DDQA6dNOT3gEoBI6_YXOwJhiPa
Basically in the file records/game/monstergamebalanceattributes.dbr all references to the first five values are replaced with the sixth (so unless there are more than six players the game applies the difficulty modifiers of a 6 player game).
And in all other files where the variable numberOfPlayers is present, it has been replaced with a 6.