Old thread but in practice there is more to it than the weight of the anchor/chain/gear versus buoy, since you have friction and the shape of the anchor involved too. I do this at least 100 times per season in depths 100 to 400 ft.
Typically what someone sees when pulling an anchor via buoy & ring is at first the buoy remains fairly in place and the anchor/line travels up through the ring, as everything starts to stretch out the buoy and anchor are getting dragged by the boat, now the anchor might be actually be exerting a force well beyond it's weight attempting to dive down to the bottom, while at the same time the ball is being planed to the top, a buoy can get pulled under in some circumstances prior to the anchor reaching the surface.
In practice for a danforth style anchor that is ~20 lbs with 50 feet of 5/16 chain (50 lbs on the high end of weight), I use a #4 sized ball, which is a 22 inch diameter ball producing 120 lbs of buoyancy.
Jon
