Having had a look at the “Installer” file with Winrar, the contents of the Balkans file are 12gb, and after installation yesterday using the installer, the total size of the Balkans directory is only 8.74gb. That must mean, not everything gets installed, or not everything gets installed as it is already present in BMS Falcon, or else almost 4gb of files gets installed elsewhere, but doing a check on the whole BMS folder, nothing else was added for that date time stamp.
But I am sure, when you install it, it only asks for about 8gb of spare space. But, it is working OK.
Only problem with installing it manually is you then have to edit the theatre.1st file and anything else that may need doing.