Ah yes.. If I was at Sea Level there would be over 15000 ft hidden, but since I'm standing at 9000 and viewing 11000, for a combined 20000, with a 15700 decline there is 4300 unhidden.. Thanks for catching the math.. Now I need to re-investigate. Someone else pointed me at refraction and a 3rd person suggested figuring out parallax..
RE: Flat Earth? - and my results