Keyboard navigation between Panels

Question

I have such XAML:

    <StackPanel TabFocusNavigation="Cycle"
                XYFocusKeyboardNavigation="Enabled"
                >
        <StackPanel>
            <TextBox x:Name="H"
                AcceptsReturn="True" TextWrapping="Wrap" 
                     ></TextBox>
            <StackPanel>
            </StackPanel>
        </StackPanel>
        <StackPanel>
            <TextBox x:Name="H1"
                AcceptsReturn="True" TextWrapping="Wrap" Text="H1"></TextBox>
            <StackPanel>
                <TextBox x:Name="L1"
                    AcceptsReturn="True" TextWrapping="Wrap" Text="L1"></TextBox>
                <TextBox x:Name="L2"
                    AcceptsReturn="True" TextWrapping="Wrap" Text="L2"></TextBox>
            </StackPanel>
        </StackPanel>
        <StackPanel>
            <TextBox AcceptsReturn="True" TextWrapping="Wrap" Text="H1"></TextBox>
            <StackPanel>
                <TextBox AcceptsReturn="True" TextWrapping="Wrap" Text="L1"></TextBox>
                <TextBox AcceptsReturn="True" TextWrapping="Wrap" Text="L2"></TextBox>
            </StackPanel>
        </StackPanel>
    </StackPanel>

And such code behind:

    public sealed partial class MainPage : Page
    {
        const string NL = "\r\n";
          public MainPage()         
{
            this.InitializeComponent();
            H.Text = "Header L1\r\n" + "Header L2\r\n" + "Header L3";
            H1.Text = "Header L1\r\n" + "Header L2\r\n" + "Header L3";
            L1.Text = "L1\r\n" + "L2\r\n" + "L3";
            L2.Text = "L1\r\n" + "L2\r\n" + "L3";
        }     
}

Now I want to nawigate using ArrowKeyUP and ArrowKeyDown. When I use ArrowKeyUP navigation flows OK. It flows line by line and next jumps to next TextBox. When I use ArrowKeyDown navigation doesnt flow. Cursor flows TextBox line by line but it doesnt jump between TextBoxes. Is it possible to fix it without hardcoding?