cacheAsBitmapMatrix not working anymore?

So, I used to think I had this working, but maybe I didn't.  I have a vector background that I want to cache for performance reasons.  My big issue is how to get my background image cached on iOS while still anti-aliasing it.

If I do the following, I take no hit on the Display List in Scout, but the image is aliased:

bg.cacheAsBitmap = true;

bg.cacheAsBitmapMatrix = new Matrix();

It's pretty much the same effect as just having cacheAsBitmap on.

If I do the following, I take a 7% hit on the Display List in Scout, but I do get it anti-aliased:

var matrixOpt:Matrix= new Matrix();

matrixOpt.scale(2,2);

bg.cacheAsBitmapMatrix = matrixOpt;

bg.cacheAsBitmap = true;

That performance hit is barely better than if I didn't do anything to the movieclip.

Does anybody know how to do this properly?  I would love to use this feature.  But right now, I think i'm doing it wrong.

Thanks!