Agregue este  code en el primero frame del swf externo.
  
Código:
 import flash.display.StageAlign;
import flash.display.StageScaleMode;
stage.addEventListener(Event.RESIZE, resizeHandler);
addEventListener(Event.REMOVED_FROM_STAGE, deadJim);
function deadJim(e){
    stage.removeEventListener(Event.RESIZE, resizeHandler); 
        removeEventListener(Event.REMOVED_FROM_STAGE, deadJim); 
    }
function resizeHandler(e:Event):void
{
	//center_mc.x = stage.stageWidth * 0.5;
	//center_mc.y = stage.stageHeight * 0.5;
}
stage.align = StageAlign.TOP_LEFT;						
stage.scaleMode = StageScaleMode.NO_SCALE;
stage.dispatchEvent(new Event(Event.RESIZE));