I do not believe that the FAA has the authority to dabble in unmanned toy flight below 500 feet.
Real planes must generally fly above 1000 feet AGL, except 2000 feet about dense crowds of people (sporting events, etc) or 500 feet in uninhabited areas.
Thus, models can always go up to 400 feet without any chance of hitting a (legal) real airplane.
Under 400 feet is like your bedroom, not the government's business.