TabItems not filling up TabControl in my XAML layout

Hi I have the following grid layout for my app and which is a simple grid with 2 cols and 3 rows defined as follows in a stripped down manner. Anways no matter how large I make row 3 with the Grid splitter none of the TabControl items fill the height of the area alloted to it vertically.

Can anybody tell me if this is most likely something to do with the UserControl (EDSDisplay) inside the TabItem, or does it have something to do with the Window's XAML?

<Grid><Grid.RowDefinitions><RowDefinition Name="row1" Height="Auto" /><RowDefinition Name="row2" Height="*"/><RowDefinition Name="BottomRow" /></Grid.RowDefinitions><Grid.ColumnDefinitions><ColumnDefinition /><ColumnDefinition Width="0.25*" /></Grid.ColumnDefinitions><Menu Grid.Row="0" Grid.ColumnSpan="2" IsMainMenu="True"><MenuItem Header="_File" /><MenuItem Header="_Edit" /><MenuItem Header="_View" /><MenuItem Header="_Window" /><MenuItem Header="_Help" /></Menu><Image Grid.Row="1" Grid.Column="0" Source="C:\temp\Capture_Navigator.png"/><Image Grid.Row="1" Grid.Column="1" Source="C:\temp\Capture_Settings.png"/><GridSplitter Grid.Column="0" Grid.Row="2" Grid.ColumnSpan="2" ResizeBehavior="PreviousAndCurrent" VerticalAlignment="Top" HorizontalAlignment="Stretch" Panel.ZIndex="1"
                  Height="10" ResizeDirection="Rows"/><TabControl Grid.Row="2" Grid.ColumnSpan="2" TabStripPlacement="Bottom"><TabItem Name="tabItem1" HorizontalContentAlignment="Stretch" VerticalAlignment="Stretch"><TabItem.Header><Grid Background="Transparent" PreviewMouseDown="TabItem_PreviewMouseLeftButtonDown"><TextBlock Text="Dummy TabItem #1"/></Grid></TabItem.Header><Border Margin="5" BorderBrush="Red" BorderThickness="1"><Rectangle Fill="Pink"></Rectangle></Border></TabItem><TabItem Name="tabItem2" HorizontalContentAlignment="Stretch" VerticalAlignment="Stretch"><TabItem.Header><Grid Background="Transparent" PreviewMouseDown="TabItem_PreviewMouseLeftButtonDown"><TextBlock Text="Dummy TabItem #2 w/ Button"/></Grid></TabItem.Header><Border Margin="5" BorderBrush="Blue" BorderThickness="1"><Button Name="btnTest" Content="MyButton"></Button></Border></TabItem><TabItem Name="tbiEDS" HorizontalContentAlignment="Stretch" VerticalAlignment="Stretch"><TabItem.Header><Grid Background="Transparent" PreviewMouseDown="TabItem_PreviewMouseLeftButtonDown"><TextBlock Text="EDS"/></Grid></TabItem.Header><local:EDSDisplay x:Name="edsEDSDisplay"/></TabItem></TabControl></Grid>