I disagree with your interpretation. Here is the exact verbage you are referencing from the AMA: A spotter should be used to assist in monitoring the surroundi

I disagree with your interpretation. Here is the exact verbage you are referencing from the AMA: A spotter should be used to assist in monitoring the surrounding airspace for manned aircraft whenever a flight is expected to exceed 400 feet above the ground and that operation is expected to be in proximity to known manned aircraft traffic such as at a mixed-use facility or within three miles of an airport. The spotter must have sufficient visual acuity and be mature enough to take this responsibility very seriously. So unless you are operating at a mixed-use facility or within three miles of an airport, you do not need a spotter to fly a model aircraft above 400ft AGL.