In this case, the most important is frame 6. It is the most stretched frame in the falling sequence. Therefore I would consider this almost as much a key frame as 1 and 7. If you have a backlight, switch it on. Put the arc path drawing on the pegs first. Then put down 1. Put down 7. Then put down a blank sheet. You should see something like this:
Now you are going to draw frame 6. Begin to sketch in the stretched ball. When stretching the ball, keep the volume consistent. The overall mass of the ball must be the same. Position it around the x drawn on the arc path. When you have finished, you will have to flip the paper to see if it moves right: