We recently deployed our first half-dozen IPv6-only customers after 6+ months of testing, using 464XLAT. It took me ages to sort all this out, so I hope someone finds this helpful. Feedback very much welcome. https://blog.brocktice.com/2017/12/27/deploying-464xlat-for-ipv6-only-clients-on-a-small-wisp-network-with-mikrotik-routers/