Just in case someone else needs to set size width and height on point marker. Here's the template. Found it in documentation but was not here.
<UserControl.Resources>
<Style x:Key="MyPointMark_Style" TargetType="t:PointMark">
<Setter Property="Size" Value="20" />
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="t:PointMark">
<Canvas>
<Path x:Name="PART_PointMarkPath"
Canvas.Left="{TemplateBinding PointMarkCanvasLeft}"
Canvas.Top="{TemplateBinding PointMarkCanvasTop}"
Width="{TemplateBinding Size}"
Height="{TemplateBinding Size}"
Style="{TemplateBinding ShapeStyle}"
Fill="{Binding DataItem.Y2S, Converter={StaticResource LocalStatusColorConverter}}"
Stroke="{Binding DataItem.Y2S, Converter={StaticResource LocalStatusColorConverter}}"
Stretch="Fill">
<Path.Data>
<PathGeometry x:Name="PART_PointMarkPathGeometry" />
</Path.Data>
</Path>
</Canvas>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
</UserControl.Resources>
<UserControl.Resources>
<Style x:Key="MyPointMark_Style" TargetType="t:PointMark">
<Setter Property="Size" Value="20" />
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="t:PointMark">
<Canvas>
<Path x:Name="PART_PointMarkPath"
Canvas.Left="{TemplateBinding PointMarkCanvasLeft}"
Canvas.Top="{TemplateBinding PointMarkCanvasTop}"
Width="{TemplateBinding Size}"
Height="{TemplateBinding Size}"
Style="{TemplateBinding ShapeStyle}"
Fill="{Binding DataItem.Y2S, Converter={StaticResource LocalStatusColorConverter}}"
Stroke="{Binding DataItem.Y2S, Converter={StaticResource LocalStatusColorConverter}}"
Stretch="Fill">
<Path.Data>
<PathGeometry x:Name="PART_PointMarkPathGeometry" />
</Path.Data>
</Path>
</Canvas>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
</UserControl.Resources>