Another option would be to use the Morph effect.
Use the effect assist window to adjust the effect so that it uses a narrow rectangular vertical band.
Then u can use layers to stagger the effect
I saw a video from Gil or Steve which explained this and another one I think which had 'arrows" zooming upwards on a mega tree ... which looked quit cool...
I managed to do something similar for my Panels , but have no idea in which sequence it is
