Hi Brian,
I haven't tried to do anything like that but it looks as if you could achieve the effect you want by highlighting the clip, clicking on 'Keyframe', then selecting 'Opacity' from the Clip Attributes drop-down menu. You should then be able to set keyframes to get different rates of change of opacity at different times.
Hopefully one of the more expert contributors will be along to give a better explanation.
Regards,
Mike
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