如何在WPF中设置较小的扩展器标题和加宽内容？

<Expander Header="Settings" FontSize="12">
    <!-- 内容区域 -->
</Expander>

<Expander Header="Settings" FontSize="12">
    <Expander.Content>
        <Grid Width="600">
            <!-- 内容控件 -->
        </Grid>
    </Expander.Content>
</Expander>

<style x:key="CustomExpanderStyle" targettype="{x:Type Expander}">
    <setter property="FontSize" value="12"/>
    <setter property="Template">
        <setter.value>
            <controltemplate targettype="{x:Type Expander}">
                <border>
                    <dockpanel>
                        <contentpresenter dockpanel.dock="Top" contentsource="Header"/>
                        <contentpresenter dockpanel.dock="Bottom" contentsource="Content" width="600"/>
                    </dockpanel>
                </border>
            </controltemplate>
        </setter.value>
    </setter>
</style>

<Expander Style="{StaticResource CustomExpanderStyle}" Header="Settings">
    <!-- 内容区域 -->
</Expander>