The Rulz say only when a ball is lost, or deemed unfit for play. 'Lost' is self-explanatory. But in the pro world where balls are rarely lost, is the pro stuck with the same ball for the entire round or entire tournament unless declared 'unfit for play' due to visible cuts or cracks?
Under the 'same ball' rule do they have to use the eggsack same ball type? Could they mix a V1 with a Vx?