I hate to cloud the issue with facts, but the fact is the vast majority of pros do not play with finely tuned rackets. You mention doubles players. Fact is, the majority of them don't do anything to their frames other than add lead and a leather grip (maybe). That's the reason you see the doubles guys pretty much all use one of 3 or 4 frames. Off the shelf frames. Fact is, Djokovic got to be a world class player through ability, not equipment. That he has tailored equipment now is really a testament to how wildly overpaid he is, not his need for same. Djokovic would be the same player he is with a stock racket weighted to his spec. At that level, it's all between the ears. And the belief that his gear is no longer a factor is between the ears. It's a benefit of making $200M/year.