Roy W,
Those are great thank you, in fact it looks like the main should strap is similar dimensions (except length) to the short end cap straps (one half of which I have). Assuming that is case think I can use the parts I have as a reference with your photos and generate what I need. I may have a question or two once I’ve made up the patterns but I think I’m good for now.
Now I just need to check the leather stock I have is long enough for at main strap..... maybe I could liberate a stirrup leather, but I’m getting ahead of myself....
Out of interest is anyone out there looking for a functional copy of these parts, it is likely to be the sort of item where a small batch isn’t materially more effort than a one off.