Shortly after I posted this, I realized that I could just double the size of each frame and that would work well enough to slow everything down.
It still seems like there should be a more dynamic way to go about this though...
I'm going to revive this thread because I have a very similar if not identical question.. So I have a movie clip with several layers inside all keyframed like I like it. However the movie seems to play too fast in the regular scene. I'd like to try and slow it down without disturbing all my keyframe work. If I could let this movie play at 20fps while the main scene played at 30 that might work, but I can't seem to get the movie framerate to work independently of the whole scene. My second idea would be to somehow 'stretch' the movie timeline so everything gets scaled up in sync... but I can't seem to figure that out either. Is there some time saving ability to do this, or do I just need to do it the hard way with trial and error??
Any help would be swell.
To answer your first question, Flash can only have 1 frame rate at a time, so all nested movie clips will share the frame rate of the main timeline.
As for stretching an existing animation, it depends on whether it's a classic or motion based tween. With motion based tweens, stretching animations in the timeline is as simple as dragging the last frame of the tween. This is a major benefit.
Editing existing classic tweens or frame by frame tweens is harder. You could manually add frames in between the existing keyframes and then and duplicate the content in the adjecent frames so that the presence of the content of the existing frames is extended to 2 or 3 or 4 frames or whatever you need instead of just one.