You might also want to consider playing around with the "Cookie Cutter" video fx plugin in combination with pan/crop and the levels mentioned above (or better yet using a levels envelope on the track). With that three way combo you can do something like pan the above track to the right (with pan/crop), then carve out a part of that to let fade through (using the cookie cutter with a soft feathered edge), then fade out some of the top track (via level envelope or event level) to let just that right part dissolve through a little. You can do some cool shit with that technique with a little patience and experimentation.