I think the thread is heading into a quagmire. The original parts are most likely reflected in the works drawings, but the practice on the line that was fabricating the items can vary quite a bit. It can also vary quite a bit by suppliers to the Club if they have received complaints and made changes to their parts as a result of those complaints made by members
The dimension I measured in post 15 was done by me on an original metric hollow axle and I had several to check. I sent the axle in the photo to the machine shop so they could verify the measurements and produce an exact copy. I also added dimensions so they could, in addition to stock axles, produce special axles and hubs that were designed for ball or ceramic ball bearings. It would not surprise me if there were small variations of the length of all of the hollow axles currently in use.
These Vincents seem to run quite well with bent parts. I doubt all of the Girdraulics we are using have perfectly straight blades. I know the steering heads (FT1/4) are all bent because I have never measured one that has not been bent. (The FT1/1 and /2's may be stiffer.) Despite all of these problems, the bikes perform well if assembled well.
I suspect what is happening is that some of these parts have gotten to a point where reassembly has started to show an accumulation of small errors that are causing problems. As someone who has stopped using the original brake shoes and the original brake plates due to their propensity to bend, I can easily jump to the conclusion that the problem here may not be the length of the hollow axle as I mentioned earlier.
As Chankly said, it may be time for some new parts. The Speet brake and the 8" brake both have plates and shoes that are much more resistant to bending. These parts should have a very long life. The new stock replacement items probably will have a long enough life, but due to their design, they will eventually end up with the same problems as the original parts you now have. Cost is always an issue, but at least you have some choices.
David