enameled steel tubs, including Americast
We have done 3 bathroom renovations in the past 7 years (moved once), and installed one Americast tub, and one Kaldewei tub in our old house (Kaldewei is a German brand that makes enameled steel tubs). The Americast was a fine tub, didn't flex when my 6'2" husband stood in it, kept a pretty nice surface, and had a look and feel quite close to cast iron. We (myself and my carpenter) brought it up two flights of stairs, something we could never have done with cast iron. We did install it over doubled joists, which is not too difficult to achieve in a limited area. In our guest bath, we installed a Kaldewei tub. I can't say enough about the beauty and ease of installation of these tubs. They are 3.5 mm enameled steel, don't flex, look gorgeous (lots of shapes, two ended if you like, center drain if you like, great grip pattern) and are easy to install, since they sit on legs. You can get at the drain/overflow system until you build a front to the tub. One of the great advantages of this brand is that their "mini" model has an angled end at the foot end. This allows a tub to fit in some pretty tight spots. Our guest bathroom was 6X7 in our old house, and we had the tub/shower combo, along with a toilet and pedestal sink, and it still felt roomy. I liked the Kaldewei so much, we are putting two of them in our new house. If I couldn't have gotten Kaldewei, then it would have been a toss-up between American Standard and a cast iron tub.