ReadyNAS, RSYNC, Windows ACLs and XigmaNAS

So, I have a new XigmaNAS server and an old ReadyNAS 10TB server (95% full). They are connected and can talk directly over a dedicated link. Sorry but it was much cheaper to build a 50TB server than buy one of the newer Netgear Boxes.
The objective is to have the READYNAS device become the backup server once the data has been copied over.

I currently use Netgear's RSYNC to auto backup from the ReadyNAS to an even older ReadyNAS (DUoV2) and all is fine. I can then mount the backup shares under windows and all the permissions are intact.

During testing I couldn't get a ReadyNAS Rsync job to log in correctly to the Xigmanas server so I've set the XigmaNAS as a client, set up RSYNC under share/network access and run a job to transfer a small share from ReadyNAS. All appears to transfer. At the root level of the share I can happily create/edit/delete documents. However at lower level directories I can read but not write anything. or I can't access some directories i.e. permissions aren't being transferred.

When I look at the permissions I can see, the ReadyNAS security list looks much more like a "normal" Windows ACL and includes CREATOR OWNER, CREATOR GROUP with owners and users listed from the ReadyNAS device. The XigmaNAS list is essentially all special permissions for XigmaNAS users and deosn't include the CREATOR permissons.

The Windows ACLs aren't complicated but I'd rather continue to use them as most of the clients used here are windows.

I think that the ZFS datasets and SMB shares are set up correctly on XigmaNAS to inherit ACLs and permissions. I can copy the same share using a windows client and all seems to be OK. So I'm guessing that it's either RSYNC itself or RSYNC combined with how the two different systems store the Windows ACLs. but reading the docs for SAMBA, RSYNC, ReadyNAS and XigmaNAS at "user" level isn't giving me a direction to try next. There's many a thread covering where it doesn't work but haven't ofund much that's helpful in a general sense or specific to these two environments.

Obviously I could use a Windows client, but tying up a windows machine to transfer 10TB over the main network rather than use the direct port to port link between the two boxes seems mad. In any case I wouldn't then have a solution for automated backup between XigmaNAS and ReadyNAS going forward.

So I'd either like to get this working or if that isn't possible find another way to copy windows shares between the two boxes.

Has anyone else done this or if you can explain or point to references that explain how either XigmaNAS or Readynas or both use (are configured for) SAMBA and RSYNC that would be helpful.

Thanks