http://www.deadly.org/article.php3?sid=20030702084202

"To be absolutely clear, the registar I've done this with is Network
Solutions. They have an 'advanced dns team' that responds to the phone
number of 1-866-345-0330 in the US. Other registars may have other numbers
or points of contact you may have to worm your way to in order to get this
done. But the bottom line is, the gtld-servers can do this."

Read on to see how you can register an IPv6 DNS server more easily.