I used the script menu. When it hits the pad, its script gets set to reduce its size until it's the size I want. At the same time, the pad sets its speed and direction to a specific predetermined path, so I don't have to worry about it not reaching the purple path. Speaking of, the final thing it does is set its script so that, once it reaches the size I want, its collision layer is changed to the layer of the path. That way, it doesn't get stopped by the path early.
