This was achieved by measuring the total length of the visible portion of the characters curve with a length of string.
May be the technical high point of the whole article.
But seriously, this is gorgeous. When I wrote a version of Pong to be displayed on an oscilloscope I coded the digits 0-9 and the letters A, E, G, M, O, R, V as polylines by tracing them out on graph paper, and that was more work than I really wanted to spend. Now I wish I had been more ambitious :)