Hi Clive,
thank you for posting this - very interesting indeed!
On my 1938 MX80 Brough I am also using cork inserts in the clutch plates instead of the original woven asbestos ones. I have the same experience - the spring pressure required to keep the clutch from slipping is strongly reduced, which is a real bonus for the left hand!
I think the only drawback is that the cork inserts are growing when they get hot:
I once lent the bike to a guy who had no experience of cork clutches. He left the bike in gear while held up in a traffic jam, and when the warming up clutch started dragging, he used the rear brake to keep the bike ad standstill and more throttle to keep the motor spinning! By the time I caught up with him, heavy smoke was coming out of the primary chaincase!!
Which meant I had to cut and fit another 84 (?) piece set of these little wedge-shaped inserts

, but the clutch has been fine ever since.
So please keep us posted with your longtime experience - I feel a cork clutch which is not abused is a wonderful thing!
Cheers
Wilfried