FluidMoveSetTagBehavior stretching Text vertically - wpf

Question

I've recently start to learn all about FluidMoveSetTagBehavior and FluidMoveBehavior using Microsoft Expression Blend and Visual Studio 2010. Following a few examples I've found on the web, I've created the below sample which works well apart from a small problem.
I have been trying to test creating an animation to show an update of a TextBlock when a ListViewItem is selected.
When an item is selected in the ListView the text does move to the TextBlock as per the FluidMoveBehavior but the text is stretched vertically during the animation phase. It then snaps back correctly within the TextBlock once the animation ends. I initially had this problem with horizontal stretching too but I was able to solve this adding a few HorizontalAlignment="Left" properties. No such luck VerticalAlignment properties though.
Xaml Code
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="1*"/>
<ColumnDefinition Width="1*"/>
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition Height="Auto"/>
<RowDefinition Height="Auto"/>
<RowDefinition Height="Auto"/>
</Grid.RowDefinitions>
<WrapPanel>
<TextBox Height="23" Name="TextBox1" Margin="4" VerticalAlignment="Center" Width="120" />
<Button Content="Add" Margin="4" Name="Button1" VerticalAlignment="Top" Width="75" />
<Button Content="Remove" Margin="4" Name="Button2" VerticalAlignment="Top" Width="75" />
</WrapPanel>
<ListView Grid.Row="1" Height="150" Name="ListView1" SelectionMode="Single" VerticalAlignment="Top">
<ListView.ItemsPanel>
<ItemsPanelTemplate>
<StackPanel >
<i:Interaction.Behaviors>
<ei:FluidMoveBehavior Duration="0:0:0.5" AppliesTo="Children">
<ei:FluidMoveBehavior.EaseY>
<QuarticEase EasingMode="EaseInOut"/>
</ei:FluidMoveBehavior.EaseY>
<ei:FluidMoveBehavior.EaseX>
<QuarticEase EasingMode="EaseInOut"/>
</ei:FluidMoveBehavior.EaseX>
</ei:FluidMoveBehavior>
</i:Interaction.Behaviors>
</StackPanel>
</ItemsPanelTemplate>
</ListView.ItemsPanel>
<ListView.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding}" FontSize="14" HorizontalAlignment="Left" TextWrapping="Wrap"
Opacity="0" TextAlignment="Center" Height="23" >
<i:Interaction.Behaviors>
<ei:FluidMoveSetTagBehavior Tag="DataContext"/>
</i:Interaction.Behaviors>
<TextBlock.Triggers>
<EventTrigger RoutedEvent="FrameworkElement.Loaded">
<BeginStoryboard>
<Storyboard>
<DoubleAnimation Storyboard.TargetProperty="Opacity"
Duration="00:00:01"
From="0"
To="1" BeginTime="00:00:00.4000000" />
</Storyboard>
</BeginStoryboard>
</EventTrigger>
<EventTrigger RoutedEvent="FrameworkElement.Unloaded">
<BeginStoryboard>
<Storyboard>
<DoubleAnimation Storyboard.TargetProperty="Opacity"
Duration="00:00:01"
From="1"
To="0" />
</Storyboard>
</BeginStoryboard>
</EventTrigger>
</TextBlock.Triggers>
</TextBlock>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
<StackPanel Grid.Column="1" Grid.Row="1">
<TextBlock DataContext="{Binding SelectedItem, Mode=TwoWay, ElementName=ListView1}" HorizontalAlignment="Left"
TextWrapping="Wrap" FontSize="14" Text="{Binding Mode=OneWay}" Height="23" >
<i:Interaction.Behaviors>
<ei:FluidMoveBehavior InitialTag="DataContext" Duration="0:0:2">
<ei:FluidMoveBehavior.EaseX>
<CircleEase EasingMode="EaseOut"/>
</ei:FluidMoveBehavior.EaseX>
</ei:FluidMoveBehavior>
</i:Interaction.Behaviors>
</TextBlock>
</StackPanel>
</Grid>
Code Behind
Class MainWindow
Private Sub Button1_Click(sender As System.Object, e As System.Windows.RoutedEventArgs) Handles Button1.Click
ListView1.Items.Insert(0, TextBox1.Text)
End Sub
Private Sub Button2_Click(sender As System.Object, e As System.Windows.RoutedEventArgs) Handles Button2.Click
ListView1.Items.Remove(ListView1.Items(0))
End Sub
End Class
Hope someone can help.