BorderSkin replacing RectanglarBorder problems

Ever since moving to SDK 4 (build 10485) I have noticed that where previous my border's were instances of RectangularBorder they are now mx.skins.spark.BorderSkin.

I was wondering does BorderSkin have the same styling support.

My problem is in the following code;

private function createBorderSkin():void

{

  var borderClass:Class = getStyle("borderSkin");

  if(borderClass != null)

  {

    _border  = new borderClass();

    _border.styleName = this;

    addChild(_border);

  }

}   

My CSS has cornerRadius, backgroundColor, borderColor values set that were previously being acknowledged.

Now ever since the borderClass instance is of type BorderSkin instead of RectangularBorder, none of the styles are being applied.

regards,

Bjorn