title: Wpf custom control template - relative font size
body: <p>I am creating a custom WPF control that let's say for simplicity sake has a vertical stack panel with a "title" TextBlock, followed by a ContentPresenter. I want the font size for the "title" to be 5 Points LARGER than the size used in the content, which is inherited by whatever container the user places this control in.</p>
  
  <p>How can I specify a font size in the control template for the header element using a relative value without exposing a property like "TitleFontSize" to the user? I want do "add 5".</p>
  
  <p>I tried using a ScaleTransform on the header text block with mixed results (the text block scaled fine but the orientation was modified - I had the text right-justified and it moved "off the control" area when scaled). Also, I am not sure if scale transform would be approprite here. </p>