Why risk moving the mirror? A good question that I try not to linger upon, because the task is only half done. Like in a baseball game where the batter streaks for first base and the fielders all move with their best speed. At the last fraction of a second, the 1st baseman stretches for the ball as the runner stretches for the bag. Only one person's call matters and that is the umpire. Say what you will, he had to make the "Judgement Call". There are so many in restoration.