The third movement is quite straightforward. Keep the tempo steady and do not over-conduct. At 7 after 3, the ascending scale in thirds is quite difficult, but slowing down more than a hair’s breadth is counter-productive. The second movement is basically in 4 except for an occasional rallentando (e.g., 4 after 3). Actually, it is the first movement that poses the greatest problems of ensemble. Where the orchestra and soloist have different and alternating rhythms (4/4 and 6/4), the danger is that one party will speed up while playing in 4/4 passages. And it can be either party.

You must listen constantly, anticipating the slightest variations while maintaining a steady, but not rigid, tempo. It is for this reason that I say that a conductor's technique is, in very large measure, in his or her ears. Identifying challenging passages in advance comes with study and practice, of course. But each work has its own set of challenges, and each performance has its own life.