IPv4/IPv6 Coexistence WG has issued "IPv6 Home Router Guideline (Ver.2.0 July 29 2010 / Translated
January 12 2012) at the following page.
https://www.v6pc.jp/en/wg/coexistenceWG/v6hgw-swg.phtml
Please refer "Reports" at the bottom of the page for details.