Silverlight 2 Point animation

I'm working with animation in Silverlight 2 and am able to get some stuff working, but I am having problems trying to animate a polygon object's points.  I've got a polygon with four points...

<Polygon x:Name="poly1"
                MouseLeftButtonDown="poly1_MouseLeftButtonDown"
                Points="100,100 200,100 200,200 100,200"
                Stroke="Blue"
                StrokeThickness="2">
                <Polygon.Fill>
                    <SolidColorBrush Color="LightBlue"></SolidColorBrush>
                </Polygon.Fill>
                <Polygon.RenderTransform>
                    <RotateTransform CenterX="150" CenterY="150" Angle="0" />
                </Polygon.RenderTransform>
            </Polygon>

I am trying to alter the 4 points of the polygon so that it changes into a different shape, size, and location.  In the following code, all of the animations work perfectly except for the last one that deals with the points.  I have tried to use PointAnimation instead of DoubleAnimation but it still throws an error when loading the silverlight object.

<Storyboard x:Name="myStoryBoard">
                <DoubleAnimation
                    Storyboard.TargetName="poly1"
                    Storyboard.TargetProperty="Opacity"
                    From="1.0" To="0.0" Duration="0:0:2"
                    AutoReverse="True" RepeatBehavior="Forever" />
                <ColorAnimation
                    Storyboard.TargetName="poly1"
                    Storyboard.TargetProperty="(Polygon.Fill).(SolidColorBrush.Color)"
                    From="LightBlue" To="Red" Duration="0:0:5" AutoReverse="True" RepeatBehavior="Forever" />
                <DoubleAnimation
                    Storyboard.TargetName="poly1"
                    Storyboard.TargetProperty="(Polygon.RenderTransform).(RotateTransform.Angle)"
                    From="0.0" To="90.0" Duration="0:0:5" AutoReverse="False" RepeatBehavior="Forever" />
                <DoubleAnimation
                    Storyboard.TargetName="poly1"
                    Storyboard.TargetProperty="Points"
                    From="100,100 200,100 200,200 100,200" To="100,300 200,300 300,200 300,200" Duration="0:0:5" AutoReverse="True" RepeatBehavior="Forever" />

Any ideas?