Support for 8" and 9" tablets

Question

Quoting Supporting Multiple Screens | Android Developers

320dp: a typical phone screen (240x320 ldpi, 320x480 mdpi, 480x800 hdpi, etc).

480dp: a tweener tablet like the Streak (480x800 mdpi).

600dp: a 7” tablet (600x1024 mdpi).

720dp: a 10” tablet (720x1280 mdpi, 800x1280 mdpi, etc).

Now I am building somewhat of a news reader app and for 7" portrait, the app is single pane; 7" landscape, dual pane (ie headlines on the left and details on the right). For both 10" portrait and landscape, it's dual pane.

From roaming the web, I've discovered that there are tablets that falls between 7" and 10". And from my understanding, any device that is in this range will use 7" layouts.

But I want devices that's at least 8" to display two panes.

So my question is, is my approach right and how do I get the dp values of tablets at least 8" (just as 7" is 600dp and 10" 720dp)?