It is annoying that after restarting Gargoyle the leases are gone, hence DNS server looses information about its hosts.
Perhaps a solution to this would be a permanent lease file, which could be located for example in /overlay/var. The change would be slightly more complicated than just reconfiguring a DNSMasq service, since /tmp/dhcp.leases is hardcoded in a number of places. I am sure it would be a good addition though.
We'll need additional config option in DHCP tab.