ApplyFilter with PixelBender does not respect rectangle clip area?

Hello,

I've been messing around with PixelBender shaders and when trying to squeeze out some additional performance, I've noticed (in Scout) that using built-in filters with bitmapData.applyFilter the "source rectangle" works as intended, but with PixelBender shader it is somewhat ignored and the whole bitmap ends up being processed.

Does anyone know how to deal with that? As in, I would really like to filter only a small part of an image.

Here is an example Flash CC project: http://adobe.ly/16pd7du