WPF set Stackpanel transparency

I need to set the background of a stackPanel transparent.  I have a rotating image that is being displayed full screen. But I need the UserControls I put in the stackpanel to show on top of the rotating images.  This used to work a year or more ago.  The code is the same. What happens depending on what order I place the controls in the xmal I get different results. 

if I have the stackpanels first the images show but I can't see any of the userControls added to the stackPanels

      <customControls:StackingPanel x:Name="panelLeft" Grid.Column="0" ClipToBounds="True" />
        <customControls:StackingPanel x:Name="panelRight"  Grid.Column="2" ClipToBounds="True" />

 <local:AdRotator x:Name="adRotatorPromo" Grid.ColumnSpan="3"  Width="1366"  Height="768" VerticalAlignment="Top" />

if I have the adRotator (custom userControl) first I get white boxes over the images where the stackpanels are and i can see the usreContols added to the stackpanel

  <local:AdRotator x:Name="adRotatorPromo" Grid.ColumnSpan="3"  Width="1366"  Height="768" VerticalAlignment="Top" />

        <customControls:StackingPanel x:Name="panelLeft" Grid.Column="0" ClipToBounds="True" />
        <customControls:StackingPanel x:Name="panelRight"  Grid.Column="2" ClipToBounds="True" />


I have tried setting the stackpanel background to the same and adRotator and that didn't help.<customControls:StackingPanel x:Name="panelLeft" Grid.Column="0" ClipToBounds="True" Background="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType=local:AdRotator}}" /> 

I've tried setting Opacity on the stackpanels but that seems to affect the usercontrols added to it.

Any help would be great,