How to inherit from, or override elements of, the Default style for a WinUI 3 control?

I am trying to learn how to use Styles most effectively in WinUI 3 (from WindowsAppSDK 1.1.1) but I'm having difficulty getting simple inheritance to work.

Consider the NavigationViewItem class. I'd like to modify the default style to bind the FontSize and Height properties. The following works in my Page XAML:

    <NavigationViewItem x:Uid="Shell_05" helpers:NavigationHelper.NavigateTo="ViewModels._05CreditViewModel"
                        FontSize="{Binding ViewModel.RootShellFontSize, ElementName=shellPage}"
                        Height="{Binding ViewModel.CurrentMenuItemHeight, ElementName=shellPage}">
        <NavigationViewItem.Icon>
            <BitmapIcon UriSource="\Images\credit.png"/>
        </NavigationViewItem.Icon>
    </NavigationViewItem>

But adding the two properties to a page resource does not (although the FontSize property works in each of the following. It's the Height that doesn't):

<Page.Resources>
    <Style TargetType="NavigationViewItem" >
        <Setter Property="FontSize" Value="{Binding ViewModel.RootShellFontSize, ElementName=shellPage}" />
        <Setter Property="Height" Value="{Binding ViewModel.CurrentMenuItemHeight, ElementName=shellPage}" />
    </Style>
</Page.Resources>

Neither does adding the style to a resource dictionary and merging. I've read over what I can find about inheriting styles and the BasedOn="" extension is an explicit way to derive from an existing style in WinUI versions prior to 2.6 (I think). Apparently, WinUI 3 does not require BasedOn. In any case, simply specifying TargetType="NavigationViewItem" doesn't work, but nor does

<Style TargetType="controls:NavigationViewItem" BasedOn="DefaultNavigationViewItemStyle">

The source code for v1.1.1 of the SDK declares a default style for the NavigationViewItem in generic.xaml, but there is no definition for DefaultNavigationViewItemStyle.

I also cannot derive from the default style using

<Style TargetType="controls:NavigationViewItem" BasedOn="{StaticResource {x:Type NavigationViewItem}}">

because x:Type is undefined.

I can do all of the bindings I want in code but I assume it's both clearer and more efficient to do it in XAML.

How do I inherit, derive from, or override a portion of the default style for a WinUI 3 control (not a custom control) in a desktop application, please?

Thanks for any help. Pointers to good XAML for WinUI 3 documentation (or books and articles) would also be greatly appreciated.