To hold the shoe in place we will use the left over soda bottle and some 1/2 inch PVC. What we will do is cut 3 pieces of PVC to act like the toes holding the shoe in place. You can also swap out shoes as they get worn out.
First take the leftovers from the 2 Liter bottle and cut a piece that is as wide and as tall as your shoe when the roof hits the 1 inch PVC. Next cut the three pieces of PVC the length of from the end of the 1 inch PVC to the end of the shoe. Since shoes curve, these three pieces will vary in size and will probably look like in picture 2. Take the pieces and glue them in the way that your shoe curves. For example, if your making a leg for your left side the smallest piece should be on the left and vice versa. Remember to look and compare the pieces to your shoe to make sure they are in the right order before gluing.