ScrollBar Thumb not working (after applying template)- WPF

Hi,

   I have a scrollbar for whichi I  am applying template and the XAML is given below. I have two questions from the below XAML. 

•     When I drag the thumb, its not moving.
•     How to increase the size of Thumb>

<ScrollBar Minimum="0" Maximum="100" Orientation="Vertical" Grid.Column="4"><ScrollBar.Style><Style TargetType="ScrollBar"><Setter Property="Template"><Setter.Value ><ControlTemplate TargetType="ScrollBar"><Grid ><Grid.RowDefinitions><RowDefinition Height="20"/><RowDefinition Height="*"/><RowDefinition Height="20"/></Grid.RowDefinitions><RepeatButton Command="ScrollBar.PageUpCommand" Content="up"/><Track Name="trck" IsDirectionReversed="true" Grid.Row="1"><Track.IncreaseRepeatButton ><RepeatButton Command="ScrollBar.PageDownCommand" Opacity="0" Background="Transparent"  /></Track.IncreaseRepeatButton><Track.Thumb ><Thumb   Foreground="Red"><Thumb.Style><Style  TargetType="Thumb"><Setter Property="Height" Value="30"/><Setter Property="Template"><Setter.Value><ControlTemplate TargetType="Thumb"><Ellipse Fill="Orange" Width="20" Height="30"/></ControlTemplate></Setter.Value></Setter></Style></Thumb.Style></Thumb></Track.Thumb><Track.DecreaseRepeatButton ><RepeatButton Command="ScrollBar.PageUpCommand" Opacity="0" Background="Transparent"  /></Track.DecreaseRepeatButton></Track><RepeatButton Content="Dn" Command="ScrollBar.PageDownCommand" Grid.Row="2"/></Grid></ControlTemplate></Setter.Value></Setter></Style></ScrollBar.Style></ScrollBar>

I couldnt see my orange color Ellipse (inside the Thumb) even after increasing hte size.

Kindly help me in above two questions.

Sanjay.