My suggestion would be, if possible, to add a function to change the master address for slave zones. As it is, if the master IP address changes, the zone must be deleted and another {slave zone name, IP address list} entered. It's nice that my end of the tunnel will have a fixed IPv6 address, which I can exploit, but it would also be nice to fetch the zone(s) over IPv4. With DHCP, my address is pretty stable (changes maybe once a year, if that), but recently my router died, and essentially the address associated with its WAN MAC address died with it (as far as me being able to claim it). Plus, if the tunnel server I'm currently using degrades in performance (let's say my ISP changes its (IPv4) routing so that Ashburn becomes a better bet than Chicago), it'd be nice to change even the IPv6 master address.
I contacted HE support January 2014 requesting this feature and received the following reply:
QuoteThis is something that our DNS administration team is looking into,
though its implementation will be in the future months. Currently, the
deletion of the zone and re-adding as a slave is the only work around
for master DNS server changes.
I guess they're still working on it :o