Hello Steve,
What you have setup is multitier system replication which is fully supported by SAP as far as I am aware.
Set up Multitier System Replication with hdbnsutil: SAP HANA Administration Guide - SAP Library
Also see page 21 in the following presentation.
To avoid a "split brain" you really should have a clustering solution in place with STONITH.
Another thing I strongly advise is that the HDB instances you install you should install with virtual addresses and only those virtual addresses should be used by your clients (studio/SAP/browser) to connect. eg: in your hdbuserstore you would add the virtual address (v<sid>xxxxx). That way you can perform some isolation with your DNS by making the original primary virtual address non resolvable to your client.
Hope this helps a touch.
KR,
Amerjit