General: Performance decrease in newer versions of Flint?

I have an old project from 2008 of an extremely simple nature - it uses a PixelRenderer as a mask to reveal a MovieClip on stage.

I have tried to port this old code to the latest version of Flint (4.x) and am very surprised that it _appears_ to run a lot slower. I would have imagined that more recent versions would be more performant, if anything, not less. So I assume there may be something wrong with what I'm doing now that wasn't wrong 5 years ago.

Here's the old code:

var renderer:BitmapRenderer;
		var emitter:Emitter;
		
		var mc_pic:MovieClip;
		
		public function Main() {
			addEventListener(Event.ADDED_TO_STAGE, init);
		}
		
		private function init( event:Event ) {
			mc_pic = this.getChildByName( "picMC" ) as MovieClip;
			mc_pic.cacheAsBitmap = true;
			
			renderer = new PixelRenderer( new Rectangle( 0, 0, stage.stageWidth, stage.stageHeight ) );
			renderer.addFilter( new BlurFilter( 6, 6, 1 ), true );
			renderer.cacheAsBitmap = true;
			
			emitter = new Emitter();
			emitter.renderer = renderer;
			emitter.counter = new Steady( 10000 );
			
			emitter.addInitializer( new Position( new RectangleZone(  mc_pic.x, mc_pic.y, mc_pic.x + mc_pic.width, mc_pic.y + mc_pic.height )  ) );
			
			emitter.addInitializer( new Velocity( new DiscZone( new Point( 0, 0 ), 5, 20 ) ) );
			emitter.addAction( new Move() );
			
			emitter.start();
			
			addChild( renderer );
			mc_pic.mask = renderer;
		}

And here's the updated version:

var renderer:BitmapRenderer;
		var emitter:Emitter;
		
		var mc_pic:MovieClip;
		
		public function Main() {
			addEventListener(Event.ADDED_TO_STAGE, init);
		}
		
		private function init( event:Event ) {
			mc_pic = this.getChildByName( "picMC" ) as MovieClip;
			mc_pic.cacheAsBitmap = true;
			
			renderer = new PixelRenderer( new Rectangle( 0, 0, stage.stageWidth, stage.stageHeight ) );
			renderer.addFilter( new BlurFilter( 6, 6, 1 ), true );
			renderer.cacheAsBitmap = true;
			
			emitter = new Emitter2D();
			emitter.counter = new Steady( 10000 );
			
			emitter.addInitializer( new Position( new RectangleZone(  mc_pic.x, mc_pic.y, mc_pic.x + mc_pic.width, mc_pic.y + mc_pic.height )  ) );
			
			emitter.addInitializer( new Velocity( new DiscZone( new Point( 0, 0 ), 20, 5 ) ) );
			emitter.addAction( new Move() );
			
			renderer.addEmitter( emitter );
			emitter.start();
			
			addChild( renderer );
			mc_pic.mask = renderer;
		}

There are only so many hours in the day! I wish I had a deeper understanding of optimization in an AS3 context, or I would offer to help.