C1ToolbarTabControl: Set width to fill

Hi,

Is it possible in the C1ToolbarTabControl to set the width to fill the C1ToolBar?

If I add tabs to the C1Toolbar without tabcontrol, i can see the border of the implicit tabcontrol stretch over the full width. Like this:

<c1:C1Toolbar>
            <c1:C1ToolbarTabItem Header="Tab1">
                <c1:C1ToolbarGroup Header="Group" >
                    <c1:C1ToolbarButton LabelTitle="btn1"></c1:C1ToolbarButton>
                    <c1:C1ToolbarButton LabelTitle="btn2"></c1:C1ToolbarButton>
                    <c1:C1ToolbarButton LabelTitle="btn3"></c1:C1ToolbarButton>
                </c1:C1ToolbarGroup>
            </c1:C1ToolbarTabItem>
        </c1:C1Toolbar>

But if I add a tab control then the border is wrapped around available Groups. Like this:

<c1:C1Toolbar>
            <c1:C1ToolbarTabControl>
                <c1:C1ToolbarTabItem Header="Tab1">
                    <c1:C1ToolbarGroup Header="Group" >
                        <c1:C1ToolbarButton LabelTitle="btn1"></c1:C1ToolbarButton>
                        <c1:C1ToolbarButton LabelTitle="btn2"></c1:C1ToolbarButton>
                        <c1:C1ToolbarButton LabelTitle="btn3"></c1:C1ToolbarButton>
                    </c1:C1ToolbarGroup>
                </c1:C1ToolbarTabItem>
            </c1:C1ToolbarTabControl>
        </c1:C1Toolbar>

Is it possible to use the tab control AND have the border stretch to fill the full width?