The acceptance window

A serve is a two-sided constraint: over the tape, short of the service line. Brody's acceptance window is the range of launch elevations that satisfy both at a given speed, height and spin. Sweep the launch angle through the flight solver and count the angles that go in.

At 187 km/h from 2.85 m with 1,800 rpm of topspin the window is about 2.2°. It narrows to 1.75° at 216 km/h, to 1.75° from 2.50 m, and to 1.5° without spin. That is the whole story of serving: the fastest servers are tall, and second serves kick.