Hello I have a question concerning a Human Sundial. I have the plans to make one and all the materials, but there is one thing that I haven't been able to figure out how to make. I have the concrete to all the hour stones, and I know what size they need to be. It's the Month stone that messes me up. I understand how it looks but I don't understand how you are suppose to make it exactly. If there is some sort of mathematical formula, something just based on the size of the sundial, or whatever it is, just please let me know. Thanks.