Flex :: Converting Sprite To Bitmapdata With A Different Registration Point And Rotation

I'm trying to convert a Sprite that I have into BitmapData so I can perform some collision detection. There are a few things about the way the Sprites are used that is making this more difficult than I expected:

The Sprite itself is a container which holds another Sprite that actually has a box drawn in it. The inner Sprite is positioned negative half its width & height so that it can be rotated from the center via the container. The container may be rotated at any angle at any given time

So my approach thus far has been attempting to draw the outer Sprite onto a new BitmapData object with a Matrix to account for the difference. Whilst I can use a Matrix to make this work for one particular rotation angle, I cannot find a way to make it work for any rotation.

Here's what I'm doing to draw onto the new BitmapData:

var p:Product = getProduct(); // Product is the container with the inner sprite
var bounds:Rectangle = p.getBounds(stage);
var bd:BitmapData = new BitmapData(bounds.width, bounds.height, true, 0x00FFFFFF);

[Code]....

Translating by the same amount as the previous example will no longer work here, and the box will still be cut off. I've looked around at some solutions posted before or suggestions from other people but they don't seem to work for me due to my container Sprite and rotation.