I am considering breast augmentation with Polytech Microthane (polyurethane) implants and I am aware that they are a bit firmer in the first 8-10 months, however do they get equally soft as polytech mesmo silicone implants after this period or they are permanently firmer?I am putting 315cc high profile under the mascle, as I have little my tissue and did not have pregnancies yet. Do breasts with silicone implants put under the muscle move and behave more naturaly than with polyurethane imlants?