Just an added tuppence worth - I had the symptoms you describe and tried various clutch plate height/orders to not much avail. Eventually got so p*ssed off that I re-fitted a stock clutch; discovered that the slipper's hub was the two part with bearings, which had largely disintegrated. Unless FBF do replacement components, that's a £800 clutch down the swannee.
Hope your problems are of the adjustment variety.