I don't think balls are either merely heavy or light. There are lots of options, like the amount of fluff or wharf on the outside. But, to your point, when Rafa and Novak were playing that final in 2012, and it started to rain, the balls got wet and the clay adhered to the balls. We actually saw that in Hamburg last week. The balls got so covered in clay they actually changed color and were harder to see on TV. In any case, when the clay sticks to the balls, it makes them heavier. So, given that we're having this RG in the autumn, when the weather is going to be colder and damper, why in the world would they chose an already heavier ball? Given that conditions might very likely make the balls heavier or lower-bouncing, anyway? Cool temperature and night conditions, (which we will have a lot of, as Paris only has 12 hours of daylight at this time,) dampness and indoors will all make the balls bounce lower, anyway. This should all favor flatter-ball hitters, and oddly, perhaps, grass players, because the surface is natural, and you get odd bounces, so improvisational skills will be prized. I'm expecting that points will be shorter, net play will factor more, and the big servers might do better than expected.
