refnrev, there is no requirement in any of the rules sets that requires the players to be set (i.e., not moving) at the moment of serve. (Perhaps your partners who are insisting the players be set at the moment of serve are football officials????
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Per NFHS Rule 6, the only requirements are that at the moment of serve, all players shall be within the team's playing area and be in correct serving order. The only problem that could exist is if a player waves arms, jumps, moves sideways or stands close to the server and the ball is served directly over the player(s) which would constitute a screening violation (NFHS Rule 6.4.1.a).
So, as long as the players do not create a screen nor move so that they are overlapping at the moment of serve, there is no problem whatsoever.
To illustrate, I was refereeing a Boys' National Qualifier this past weekend and, in one match, the right front player on the serving team broke to his left as the server was tossing the ball. By the time the ball was contacted, the RF was not only overlapping the center front, but he had also overlapped the left front. Of course, I whistled the overlap as soon as the ball was contacted and, I am happy to say, that player did not do that during any of the remaining matches that I had their team during the rest of the day.