Settings a negative Top Margin on the RibbonWindow content are over the Title Bar

Hi,

I have a test app using a RibbonWindow. If i set the content to have a negative Top margin, it shows up the Title Bar overlapping it. The Microsoft WPF Window control is handling it correctly where the content are beneath the Title Bar.

How should i make the RibbonWindow work as the MS Window? 

Here is a sample code:

<ribbon:RibbonWindow x:Class="AnythingGoes.TestWindow"
                                  xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                                  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
                                  xmlns:ribbon="http://schemas.actiprosoftware.com/winfx/xaml/ribbon"
                                  Title="TestWindow" Height="300" Width="300"
                                  WindowStyle="ThreeDBorderWindow">
               <StackPanel Background="Green" Margin="0,-20,0,0">
                        <Label Content="Item 1" Height="30" />
                        <Label Content="Item 2" Height="30" />
                        <Label Content="Item 3" Height="30" />
                        <Label Content="Item 4" Height="30" />
                        <Label Content="Item 5" Height="30" />
                        <Label Content="Item 6" Height="30" />
                        <Label Content="Item 7" Height="30" />
                        <Label Content="Item 8" Height="30" />
               </StackPanel>
</ribbon:RibbonWindow>