I am trying to get the RadPane tabs to scroll when overflowed, but it isn't working. I followed the example here, but it still does not scroll when enough tabs are made visible that exceed the visible width of the tab space. I am using a User Control for the tab header content instead of the standard String.
<telerik:RadDocking.DocumentHost>
  <telerik:RadSplitContainer Orientation="Vertical">
    <!-- Main Content -->
      <telerik:RadPaneGroup x:Name="PaneGroup1" 
                            ScrollViewer.HorizontalScrollBarVisibility="Auto"
                            DropDownDisplayMode="Visible">
        <!-- Schedule -->
        <telerik:RadPane CanUserClose="False" x:Name="RadPane_ScheduleItems" IsHidden="True"
                         telerik:RadDocking.SerializationTag="ScheduleItems.HeaderObj">
          <telerik:RadPane.Header>
            <uc:RadPaneHeader x:Name="RadPaneHeader_ScheduleItems"
                              Header="Schedule Items" />
          </telerik:RadPane.Header>
            <uc:ScheduleGridView x:Name="ScheduleItems" />
        </telerik:RadPane>Tabs before and after are attached.

Hello Johnathan,
I tried reproducing this behavior using the UserControl that you provided, however, I was unsuccessful. On my end, a scroll viewer appears when the number of pane instances exceeds the visible width.
I have attached the sample application that I used for testing, so, could you give it a try?