It seems like you want a panel that doesn't move at all. So then the question is.. why even use a DockPane for that? 
I think Divya is suggesting that you just use a regular panel or UltraPanel control. That way it will not be docked and there will be no way for the user to move it or add tabs to it. If you need the pane to be collapsible, you could use UltraExpandableGroupBox which allows expanding and collapsing. 

If you must use a Dock pane, then be aware that there are probably a bunch of other undesirable behaviors you will need to deal with. For example, I suspect that in addition to allowing the user to add a tab into it, they can also place another pane BELOW it, which will also cause it to shift position. I don't think AllowDragging will prevent that - the user can still drag other panels into positions that will force the panel on the bottom to move. 

You might be able to handle that via the events of the DockManager. Perhaps there are some cancellable events and you could detect the case when the bottom panel would move based on the current drag/drop operation. But even if that is the case, it will not be easy to detect and the user will not know they can't drop the panel into that position until after they try. So I don't think that's a feasible solution. 

Divya, I am not sure what you mean by an expansion panel.  By looking at the code, I see that DragManager.PaneLocator.FindPanelElement is what finds the drop target when dragging.  I will like to add a setting to DockAreaPane or DockAreaPane.Setting that FindPanelElement will check to determine if the DockAreaPane is a valid target.  Is that reasonable?  If so, what do I need to modify to make that happen?