In Silverlight 3, it appears that the AreaDataPoint template ignores any size set in its ControlTemplate.
<ControlTemplate TargetType="chartingTK:AreaDataPoint">
    <Grid x:Name="Root" Opacity="1">
<!-- Width and Height are ignored -->
        <Ellipse Width="75" Height="25" 
                    StrokeThickness="{TemplateBinding BorderThickness}" 
                    Stroke="OrangeRed" 
                    Fill="{TemplateBinding Background}"/>
    </Grid>
</ControlTemplate>
Does anybody know of a workaround?