WPF Move text "outside" the boundaries of its own element - wpf

Question

I am making a LinearGauge control with an ItemsControl. I would like to show the boundaries labels exactly at the center of two bars. I'll try to depict my problem in the screenshot below:
Thus, the labels should all move a few pixels to the right. But the problem of course is, is that the element boundaries are where the next colored bar starts. So I want to move the label "while ignoring the element boundaries".
Is there an easy trick to do something like that?
The xaml I have so far:
<ItemsControl
Grid.Row="0"
Grid.Column="0"
ItemsSource="{Binding Elements}">
<ItemsControl.Resources>
<DataTemplate DataType="{x:Type local:HorizontalGaugeElement}">
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="Auto"/>
<RowDefinition Height="Auto"/>
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="Auto"/>
<ColumnDefinition Width="*"/>
<ColumnDefinition Width="Auto"/>
</Grid.ColumnDefinitions>
<Rectangle
Grid.Row="0" Grid.Column="0" Grid.ColumnSpan="3"
Height="30"
Fill="{Binding Color}">
<Rectangle.Width>
<MultiBinding Converter="{StaticResource BoundsToWidthConverter}">
<Binding Path="Lower"/>
<Binding Path="Upper"/>
<Binding RelativeSource="{RelativeSource AncestorType={x:Type ItemsControl}}" Path="DataContext.ValueToPercentage"/>
<Binding RelativeSource="{RelativeSource AncestorType={x:Type ItemsControl}}" Path="DataContext.GaugeSize"/>
</MultiBinding>
</Rectangle.Width>
</Rectangle>
<TextBlock
Visibility="{Binding ShowLowerBoundary, Converter={StaticResource BooleanToVisibilityConverter}}"
Grid.Row="1" Grid.Column="0"
Text="{Binding Lower}"
Margin="5, 0, 0, 0">
</TextBlock>
<TextBlock
Grid.Row="1" Grid.Column="2"
Text="{Binding Upper}" TextAlignment="Right"
Margin="0, 0, 0, 0">
</TextBlock>
</Grid>
</DataTemplate>
<DataTemplate DataType="{x:Type local:VerticalGaugeElement}">
<!-- similar story but then vertical -->
</DataTemplate>
</ItemsControl.Resources>
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<StackPanel Orientation="{Binding IsHorizontal, Converter={StaticResource BoolToOrientationConverter}}"/>
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
</ItemsControl>