Silverlight and Unexpected Font Sizes

Question

Someone please teach me to fish here...

I'm just learning Silverlight and have ran into a few situations where the font size actually used is drastically different than I would expect. There's probably something conceptual that I'm missing.

Case A

In one instance, I have defined a user control that presents a Label to show text. If one clicks on the label, the label (that is in a stack panel, in the user control) is replaced with a TextBox. When used at the top of a page (as in the example below with lblName) the label text is very small (around 8 points). When clicked on, the text box that replaces the label uses the specified fonts size. That same user control, used in different parts of the app, uses the same font for Label and TextBox.

<Grid x:Name="LayoutRoot" Background="White">
    <Grid.RowDefinitions>
        <RowDefinition Height="33" />
        <RowDefinition Height="267*" />
    </Grid.RowDefinitions>
    <StackPanel Height="Auto" HorizontalAlignment="Left" Name="stackPanel" VerticalAlignment="Top" Width="Auto" Grid.Row="1" />
    <my:EditLabel Height="33" HorizontalAlignment="Left" x:Name="lblName" VerticalAlignment="Top" Width="Auto" FlexText="{Binding Name, Mode=TwoWay}" FontSize="20" MinHeight="24" />
</Grid>

Case B

I'm using the LiquidMenu.Menu control to pop up a menu when a button is pressed. The font looks huge compared to the rest of my page (maybe 36 points?). I tried forcing it to a very small by explicitly setting it to 8pt, but that had no effect.

   <Grid x:Name="LayoutRoot" Background="{x:Null}">
        <StackPanel x:Name="labelStackPanel" Orientation="Horizontal">
            <TextBlock Height="24" HorizontalAlignment="Left" Name="labelText" VerticalAlignment="Top" Width="200" Text="(Value Goes Here)" />            
        </StackPanel>
        <liquidMenu:Menu x:Name="popupMenu" Canvas.Left="40" Canvas.Top="40" ItemSelected="MenuList_ItemSelected" Visibility="Collapsed" Height="Auto" FontSize="8">
            <liquidMenu:MenuItem ID="delete" Icon="Images/Delete10.png" Text="Delete" Shortcut="Del" />
            <liquidMenu:MenuItem ID="exclusive" Icon="" Text="Exclusive" Shortcut="Ctrl+E" />
            <liquidMenu:MenuItem ID="properties" Icon="" Text="Properties" Shortcut="Ctrl+P" />
        </liquidMenu:Menu>
    </Grid>

Answers to these specific issues are great, a new way to think about this type of issue so that I understand how to control font size is better.