MicroStation documents shared to Windows clients from Leopard Server w SMB

I would like to concur that SMB shares and permissions are still a problem in 10.5.6 Server. For example I create a shared folder and set the POSIX permission to admin R+W, Marketing (a group) R+W, Others R. I connect to the share via SMB (I am a member of group Marketing) and create a Microsoft Word document, save and close the file. My colleague (who is also a member of the Marketing group) then connects via SMB to the shared folder and tries to open the file. It opens as Read-Only so cannot save any changes to the Word doc back.

Note also I have set the SMB default permissions for new files and folders (under protocols in Server Admin) to be Owner Read and Write, Group Read and Write, Everyone Read only.

On the advice of another thread I checked /etc/smb.conf and under 10.5.6 the line acl check permissions = no is already set under Global. NB I am not using any (explicit/additional) ACLs anyway.