Michael,
The unwrapping that he is after would be if he had "Cylindrical stock" loaded into a machine that would rotate (or 4th axis) with th "Y" moves. So if you think of his flat surface as that, then he is on the right track but I dont think his theory allows for the extra length in the cylindrical unwrap.

Danny is asking the appropriate question which is something you answered for me and provided the functions to produce the conversion from the input values. I'll find the thread and post it for Danny. This was the "Draw arc by length" instead of degrees thing you answered for me.