setProperties() method problem

[Eurig Jones]

I'm trying to create my own custom tag extending UIComponentTagBase. 
with a boolean property called "whiteOnBottom"...

<m:board whiteOnBottom="true" />
...when does the setProperties method actualy get run? How do I update 
my components value when the property is changed?? Changes to the 
'whiteOnBottom' value just dont seem to register...

protected void setProperties(UIComponent component)
{
   super.setProperties(component);  
   setBooleanProperty(component, "whiteOnBottom", whiteOnBottom);
}

Thanks!
Eurig