What does mache taste like?
Flour and Water mixed together, or wall paper paste. :]
Add more paper mache. If the paper mache is too heavy and you can't create the right sized breasts for your taste, then you should build a stronger base using chicken wire. It all depends on how big you want them. If they are larger than a small trash can, then you should probably go to Lowes and buy some wood and large gauged wire to support the breast material.
Paper-mache is biodegradable, meaning that it will decompose and have no negative impacts on the environment. Other than that property, paper mache does not seem to be in any other way helpful to the environment, as it is aesthetically displeasing to look at, and is not a strong building material nor a reliable one, as it "melts" in water like cardboard.