I discovered a change in some recent version of ProFTPd - I used
Umask 0007 to remove permissions to "others" but it kept my SetGID directory flag - which is what I wanted.
In recent version (1.3.4) my permission system stopped to work. I am unable to convince ProFTPd to set SetGID flag on newly created directories.
In documentation they say "base-mode" for creating directories is 0777 and
UMask allows only to remove permissions.
How to make it set SetGID bit on new directories, that is permissions 2770?