I got to looking at the mazzocchio on that guys head and started fooling with the object. I discovered that in order to make the lathed 6-sided object that revealed a center space in the orientation shown in the Uccello wireframe — that the hexagon could not be a regular shape. The diagonals have to be twice as long as the verticals. These guys were crafty — as a headpiece, they were employing a distortion inorder to telegraph the perspective to a street level observer. Nice tweak!