Thanks for the reply. Bonding and netbalancer have worked very well in trials. I am keen to setup bonding to multiple remote sites and establish inter-site routing in addition to internet routing. Initial tests are very promising and ZS is excellent in its capabilities.
The need to setup the central or head router without specifying the remote peer IP address was very important, especially for dynamic DNS and especially for NAT router/firewall configuration.
I assume I simply set one VPN end as server and do not specify the remote IP address. At the client end I then specify the IP address of the server. As long as I use a unique UDP port for the VPN and same port at each end it should be fine? At this stage I am using PSK for simplicity.
BTW Thanks for all the great work you are doing on ZS. Much appreciated.