I think level 0 determines the frame rate of all levels when loading movies on top of each other. So if your base movie frame rate is 15fps, all movies should play at 15fps.
Now what effect will it have if you load a movie that was made with a frame rate of 30 fps? I think your second movie will run slow-mo... and if it was done at 7fps, then it should be accelerated! Worth experementing!
May the frame rate be with you!
;-)