Re: roller stabilizer or flopper stopper
Mine are about 18" in diameter, the kind you can buy at a marine store. There's 4 along each line, about 4' apart, with a weight at the bottom. The crucial part is the weight at the bottom - that's essentially an anchor that isn't stuck in the ground but counter-balancing the motion. It has to be really heavy.
They don't work that great in choppy or rolly spots. Probably help to keep the boat stable in stable conditions
1985 Catalina 30 Std Rig "A Cenoura"