[Samba] Samba4: s3fs sticky bit file ownership problem

[steve]

Hi
I want all files created in a share to be group owned by a group called 
staff. To do this I have a share called reports which is chmod g+s staff:

drwxrws---+ 9 root staff 4096 Jun 18 11:15 reports

If I create a file from Linux, the sticky bit works:

-rw-rw----+ 1 steve2 staff            0 Jun 18 10:57 stevelinux.txt

If I create it under windows, it doesn't:

-rwxrwx---+ 1 steve2 Domain Users     0 Jun 18 11:15 stevewin7.txt
-rwxrwx---+ 1 steve2 Domain Users     0 Jun 18 10:59 stevexp.txt

The file takes on the group of the creator, Domain Users in this case.

This is fine whilst the files stay inside the share as they are 
protected the directory being for staff only, but it becomes a problem 
when we need to move them around.

There is also a group rw acl set but removing it makes no difference.

Any ideas for a fix or workaround?
Cheers,
Steve