Phaedrus, that makes perfect sense...in the mind of a bureaucratic official. I gotta' get out of this. You guys are scaring yourselves to death. Bottom line? Use common sense. It's your best friend.The original rationale for 400 feet was that in general manned aircraft will be at or above 500 feet agl. 400 feet for models, etc. gives a 100-foot buffer between the two, manned/unmanned.