Well, there are some quite big models out there. I was flying down the Welsh coast at about 500 feet once (with due caution re. paragliders, being able to reach fields/beach etc...) when I saw a radio controlled aircraft at a disused field climbing vertically to well above my level.
You can actually control aircraft and drones quite well even when they're a dot in the sky - by using gentle combinations of pitch/turn you can work out whether your aircraft is facing towards or away from you, and which way up it is. It's more an emergency procedure than a way I enjoy flying them, though.