I will soon be fitting a new acrylic bath. My sister recently had a similar bath fitted by a plumber, and he used expanding foam beneath the bath to add extra support. He built a 'frame' beneath the bath and then 'filled it' with expanding foam. The bath certainly seems to be far more solid than just using the metal support legs provided, and I guess the water would stay hotter, longer. Has anyone used this system, and what are the pitfalls (other than getting foam everywhere!!