I went and looked in my papers on starter-generator, I don't have any specs, ---I don't even have original new diameter (I can get that from NOS armature I have)
A lot can be taken and still work, look at the end ,many times the remaining thickness can be seen, they are thicker in the center, sort of a K shape where they are clamped to the hub
it should be turned so the mica is cut to the same level as the bars, do not undercut between the bars,
The Citroen can use the same drive as the model A---I have a traction too