The first thing that I hear about kick serves that are used as second serves is that you should not slow down the racket.
That lead me to wonder whether you should not only not slow down, but actually accelerate more for kick serves than flat serves.
With a kick serve, the momentum of the racket will give as much vertical vector to the ball as horizontal vector.
If the vertical vector will bring the ball down into the service box and provide a higher margin of error, can you afford to swing the racket even faster than with a flat serve, so that the loss of pace as compared with a flat serve is minimized?
That lead me to wonder whether you should not only not slow down, but actually accelerate more for kick serves than flat serves.
With a kick serve, the momentum of the racket will give as much vertical vector to the ball as horizontal vector.
If the vertical vector will bring the ball down into the service box and provide a higher margin of error, can you afford to swing the racket even faster than with a flat serve, so that the loss of pace as compared with a flat serve is minimized?