I realized that the trajectory change could also affect the landing time for cannon_ball. For example, if we take a target, without the changing trajectory, the cannon_ball may only take like 3s to land and hit the target, but if we change the trajectory to make it more curved, it can potentially make the cannon_balls spend a long time to land and hit targets.
Therefore, I calculated a bit and made some adjustments so that the new landing time for cannon_balls can stay the same as the original ones.