Adding Subitems / Flyout menus to RadDropDownList

Ivan,

I tried moving to the PanelBar approach, and even the TreeView approach but both caused a problem I couldn't figure out how to overcome. When they are expanded they push the content below them down, whereas the DropDownList overlays the content below it. Am I missing a setting somewhere or is there a better tool for what I'm trying to do? Basically I want a dropdown with the ability to present hierarchical lists and I don't want the content pushed down as it opens. 

I've attached 2 screen clippings of what I'm trying to express.

Thanks