For what it's worth, HBD owner knucklebones runs an internet radio show in which he covers HBD news and various worlds. He's assisted by another HBD owner, tomjames, who puts together Power Rankings for various worlds and publishes them on their website. Last night (11/24/2010), Mantle was covered by knucklebones on his radio show and the Mantle Power Rankings were discussed.
If you're interested, you can listen to the radio show here:
Actual news about Mantle starts at around 20 minutes into the show.
If you just want to view the Power Rankings, you can see them here: