I had the oval ring on mine (1917 house, owned from '81 to '03). It used three anchor points to walls (tub sat in a corner). I was concerned that the fourth corner would sag, so I added a hanging post from the ceiling. All of these fittings were available by ordering together with the ring.

We then used (I think) 4 vinyl curtains, one of which closes across the front, the others were more or less stationary for the other three sides.