Parade ‘choreography’ can help too. Not sure whether it’s still the case but the IOT graduation flypast used to take place during a general salute, which was preceded by a minute or two of standing at ease. This was ‘flex time’ for any earlier overrun. A SNCO attendant at one end of the audience would signal the parade commander at the appropriate time to order the general salute such that the flypast coincided perfectly.