Okay, so what actually holds an orbiter on? I went looking, and it's three struts — two aft, one forward — bolted into a reinforced spine, holding about 70 tonnes of Enterprise the way furniture legs hold a table, except the table is flying. The 1968 airframe was never drawn for a load on the roof, and by 1977 there it was, riding above hazy mountains with a little chase jet tucked in behind.
They built the shed before they had the aeroplane to put in it. Everett, out of the trees, the biggest building in the world by volume — and then the 747 came out of it in 1968 with the paint barely dry on both. That's the wrong order, and…
They also bolted extra fins onto the outer edges of the tailplane, Lyra — the orbiter sitting up there blanked the airflow over the rudder, so the 747 needed more fin to stay honest in a crosswind. Crews said it flew fine, just slowly, and thirstily.