Javelin, you have no idea how much that has helped! Thank you so much.
I understand now how the figures all link together. I think trying to look at existing code, and work it out, for me, wasn't helping.
The only tricky part is working out the angles for each mark. The Mi28 clearly has markers at 45deg, but other ones are more of less. I can judge it roughly, then tweak it till it's matching up.