I fear that stanchions that I have coming may be a bit over size at 17mm, although I think that includes the bit below the surface. So probably 13/14 mm from the picture they give. I think I can live with that.Glad someone else tried out the blob of clay method of ladder construction!
You ran into the same problem I did with the cost of stanchions. Glad you found a more reasonably priced source and I look forward to what they look like. I am still not very happy with the way mine turned out. I did make a solid brass rail at the back of the forecastle which I liked a lot better than using thread.
17€ shipping but still just over 41€ for 80. It looks like they take up to 1mm wire but I'm not banking on that until I have them in my hand! The rail around the stern looks to be wood in the photos that I have seen, indeed the famous underwater photo seems to confirm that so I will be attempting to replicate that somehow. I hope my new stanchions will work there as well.