Thanks for the replies, I actually just finished setting up 2 VMs to test this - it fails to and from the backup fine and performance is good.

I wasn't aware of the states issue, so I checked, and right enough it's not syncing to the backup.

Does this mean that in the event of a failover, traffic would need to be reestablished? If that's the case, I can live with this until it's fixed.

Unfortunately I've just ordered 3 net6501, so am stuck with them for a while!