Created Issue: Making ExpanderView.Items left spacing as constant [10550]

I am using Expanderview like this

<toolkit:ExpanderView >
<toolkit:ExpanderView.HeaderTemplate>
<DataTemplate>
<TextBlock Text=""/>
</DataTemplate>
</toolkit:ExpanderView.HeaderTemplate>
<toolkit:ExpanderView.Items>
<StackPanel>
.....my contents
</stackpanel>
</toolkit:ExpanderView.Items>
</toolkit:ExpanderView >

I want to show the expanded content in the same level as that of Header but by default the Items contents are started with some left margin and what i noticed is if the header is too big then this left margin is also getting increased.
Is there any way to avoid the left spacing of the Expanderview.Items .
I want to keep Items exactly in the same level of header (dont want to show that to right of header)
Yhanks