Having trouble loading swf's into main movie

I have a bunch of swf files that are supposed to be background animations for my movie. They look perfect at 640x480, but at any other dimensions, they look terrible. 640x480 is the size of the stage they were made on.

The problem I am having is that I am loading them into a stage bigger than 640x480. Is there a way I can load them behind a mask? Or maybe just put a frame around them?