If I'm not mistaken you need to use layout-sw720dp
etc etc, going by screen width.
I assume you have calculated the correct pixel to dp for these screens. For exmaple, I have a Nexus 7 and I know it takes drawables and layouts from layout-sw600dp
not 720dp. 720dp is for 10 inch screens. Work from screen width. Your error here is picking the wrong folder.
Of course look here too because it is packed with information, it will provide everything you need: http://developer.android.com/guide/practices/screens_support.html