Disabling "Pin Tab" from context menu

I have a document window that has a context menu item of "Pin Tab" that I'd like to remove.

I can disable or remove everything else from this context menu, but no matter what I try, all I seem to be able to do is effect the Pin icon on the tab of the document.

This is a selection of what I'm doing. I'm trying with these lines <docking:TabbedMdiHost HasTabPinButtons="False" HasTabCloseButtons="True">
<docking:AdvancedTabItem CanPin="False" /> to get things the way I need as this is the closest I think I have to the answer. But bar building my own context menu and pointing my solution at that. I'm not getting anywhere.

<DockPanel Grid.Row="1" Grid.Column="2">
          <core:ViewInjectionDockSite x:Name="dockSite"  Background="#EBEBEB"
                    DocumentItemsSource="{Binding DockPanel.OpenDocuments}"
                    DocumentItemContainerStyle="{StaticResource DocumentItemStyle}"
                    ToolItemsSource="{Binding DockPanel.OpenTools}"
                    ToolItemContainerStyle="{StaticResource ToolItemStyle}"
                    CanDocumentWindowsFloat="true"
                    AreDocumentWindowsDestroyedOnClose="True"
                    core:DockSiteViewModelBehavior.EventAggregator="{Binding EventAggregator}"
                    core:DockSiteViewModelBehavior.WindowManager="{Binding WindowManager}"
                    core:DockSiteViewModelBehavior.ActiveDocument="{Binding DockPanel.ActiveDocument, Mode=TwoWay}"
                    core:DockSiteViewModelBehavior.ActiveTool="{Binding DockPanel.ActiveTool, Mode=TwoWay}"
                    core:DockSiteViewModelBehavior.IsManaged="True">
            <docking:SplitContainer>
              <docking:SplitContainer>
                <docking:SplitContainer Orientation="Vertical">
                  <!-- LEFT TOOL UPPER -->
                  <docking:ToolWindowContainer x:Name="LEFT_UPPER_TOOLS">
                    </docking:ToolWindowContainer>
                  <!-- LEFT TOOL LOWER-->
                  <docking:ToolWindowContainer x:Name="LEFT_LOWER_TOOLS" >
                  </docking:ToolWindowContainer>
                </docking:SplitContainer>
                <docking:Workspace >
                  <docking:TabbedMdiHost HasTabPinButtons="False" HasTabCloseButtons="True">
                    <docking:AdvancedTabItem CanPin="False" />
                  </docking:TabbedMdiHost>
                </docking:Workspace>
              </docking:SplitContainer>
              <docking:SplitContainer Orientation="Vertical">
                <!--RIGHT TOOL UPPER-->
                <docking:ToolWindowContainer x:Name="RIGHT_UPPER_TOOLS">
                </docking:ToolWindowContainer>
                <!--RIGHT TOOL LOWER-->
                <docking:ToolWindowContainer x:Name="RIGHT_LOWER_TOOLS">
                </docking:ToolWindowContainer>
              </docking:SplitContainer>
            </docking:SplitContainer>
          </core:ViewInjectionDockSite>
        </DockPanel>