Very good points. Particularly about the surfaces. Clearly clay was a much more important surface in the 70s than today. Hard courts did not began to acquire their current status until the US Open switched to it, and later the AO. Today the balance is very heavily tilted toward hard, of course, to the point where clay is almost seen as a less worthy surface, and the green clay events have almost completely disappeared in the US and are disappearing elsewhere also. This, along with the disappearance of grass from the AO, is one of the most regretful developments of tennis since the 80s. Much more than the change in racquet technology I think. The human body did not evolve to prance and bounce on flat rocks, but rather to glide and dance gracefully on the soft earth and the cushy green grass. Cement is an abomination and an insult to the art of tennis.