Kerry
I am unable to answer your question, but my experience over many years, since 1965 to precise, is this, a bad Vincent clutch is a most dreadful thing, it can slip, grab frighteningly aggressively, and back in the day it could fail completely if the primary clutch destroys its corks or the one piece Ferodo clutch plate disintegrates. Happily now we have excellent bonded primary clutch plates, but an original Vincent clutch, using the correct component parts, and set up correctly is a thing of sublime beauty in operation. I have experienced the very worst and the very best of the Vincent clutch.
Mostly I have assembled my own clutches, with the exception of the shoes, and I prefer if possible to use genuine Stevenage factory shoes, bored and bushed if worn oversize, and the plunger housings reclaimed, and then relined and the plungers set up on a jig.
In the past I have entrusted this work to Maughan and Sons, Bob Culver and The Godet Workshop, all have done excellent work for me.
The only real trouble I have had recently is the tang snapping off the C45 spring, and then the C20 nut unwinding itself, resulting in the loss of clutch disengagement at the lever, this might be due to an underlying problem of spline wear on the clutch shaft, or the clutch shoe carrier, or both, but I have solved this problem completely by tying the C20 nut to the slots in the shaft using a very close fitting key, retained by the C45 spring, you should be able find the details on one of my posts relating to clutch problems, it has been referred to as a bodge, but it works, and I am no longer reliant on very thin spring wire tang that has been bent at a right angle when cold to form a crude key. I spoke to a retired friend of mine who worked in the spring industry for many years, he took one look at a new C45 spring and condemned it, his comment was "of course the tang snaps off, what would you expect, it has been bent when cold, and then you can't de-stress it without destroying the spring"
Good luck with your clutch.
Peter