Robin,
there is only one spacer in between the two parts of the nut. They look to be the same type as the ones in your photo apart from the spacer being in two halves.
I do like the idea of sprung washers though. This would allow the two halves of the nut to go together tightly enough to work correctly and allow for a little bit of adjustment to align them correctly. I think I will modify them before I go any further with my build.
I am still trying to think up a good idea for replacing the seals/screw cleaners on the nuts. If anyone has any ideas they would like to share :whistling:

Ian