The most important thing that can be said about securely mounting bracketing is this: Whatever you attach the bracket to MUST be rigid to the shaft when you are not attaching to the shaft itself. When the bracket is secured and the laser/emitter is attached to it,  rotating the shaft causes the bracket to rotate along with the laser like the spoke of a wheel. Regardless of the laser’s distance from the shaft centerline, as long as everything is tight, the invisible circle that the laser traces as it is rotated has the same rotational centerline as the shaft. Make sure that everything is tight.