Thx. I updated my post with a link to my new question

Cool. And mentioning X will be enough to spare me the 'closed-as-dupe' fate?

Ah, there we go ... What about speeding up connection start by 50% where there is no IPv4 anyway? Yes, a local DNS cache would help, but disabling AAAA even more so, in particular where upstream DNS is laggy. Assume that i'd (re-)enable AAAA when/where IPv6 is available.

I will do that. At the same time i want to allow people who try to implement Y for other reasons to find my question.