Question frequently arises : how large should you scan around listener head position ? Move in all directions, even height, but avoid to be too near of a reflecting surface, ie stay a bit higher than the back of the chair.
I would scan within about +-15° off axis, that is nearly 50cm in all directions for a loudspeaker at 2m and 100cm at 4m.
Remember that for a home audio system, the MMM scan is mainly to smooth out reflections and not to average for more listeners.