On Sunday I did somewhere around 140-150 miles on the road trial. That was at least a 30 mile round trip to get to the start/finish, plus 90 miles for the 2 road trials, plus some for getting lost!
The weather was variable throughout the day, being damp in the morning and sunny in the afternoon. The roads varied from reasonable B roads to unmade dirt tracks.
All in all, the NF went really well, but most importantly, the clutch did not slip once. I had one moment where I stalled the bike as I was in gear and couldn't adjust my grip on the clutch lever. It was just a touch heavy at that moment. But during the rest of the day it wasn't a problem.
Therefore I can declare the clutch cured.