Portable Solar Dial

Based on a description in an old (1984) education magazine I build a virtual replica of a portable sun dial which was inspired by a medieval portable sundial from Canterbury. This device is also known as a "Shepard's Dial".
What I originally planned to do was make a temporal or 12-hour sun dial making it a decorative object only. This is a sun dail for modern equal hours, the example is for 52 degrees latitude, northern hemisphere. The OpenScad file is included and be set for different north-south locations.
I tried to base the dimensions on proper calculations, but couldn't get it right. It looks like the original, so I did something right :-). A smarter person than me may find the proper solution.

Usage:
The object requires a thin pole stuck through the proper month hole (roman numerals) until it reaches the opposite hole. Then orient the pole to the direction of the sun, so a vertical shadow appears. The end of the pole shadow should indicate the natural hour.

If the weathe