Hi Christopher Jenkins,
Sorry for the late response.
If you want to put a close button you can do it in the HeaderTemplate. You will have to add handler for the click event and then (hide/close) the pane (commands will be perfect here).
DockumenHost (the new name of DockumentHostContent property) only purpose is to separate the content area of RadDocking (plus some other restrictions like not showing the PaneHeader control and changing the pane appearance).
Right now we do not support adding custom buttons in document host area. We will consider adding this feature for the next version.
Thanks for your feedback. Let me know if you need more information.
the Telerik team