The problem is that ParentBarItems are never really clicked and so if you set thier IsRecentlyUsed property to false it will always be hidden when partial menus are being used.
Ideally I would like a ParentBarItem to be shown in a partial menu if any of it's children has it's IsRecentlyUsed property set to TRUE.
By adding the following piece of code to the ParentBarItem class this can be achieved.
public override bool IsRecentlyUsedItem
foreach(BarItem item in this.barItems)
base.IsRecentlyUsedItem = value;
Maybe this could be included in the next release?