Larry,
I have a diaphragm in my 15/6. These are the main elements …
https://www.dropbox.com/scl/fo/lbngaurj6g5w6oic9f45b/AAexxx9NHaFd2Q-4DlvBXwY?rlkey=m0puitvlacca1ayo99y3b6jf7&st=sb9345bj&dl=0
However, it did require a different flywheel to replace the original bi-plate unit. Mine is actually a newly made flywheel which came from a chap who had it “spare” and unwanted, on the shelf. Unfortunately, I don’t know how it compares with a later, original, single disc flywheel.
In honesty, I don’t think it makes the clutch operation much lighter but it does haveo a ball thrust race and that is definitely better for wear than the carbon original.
B…..
Larry Lewis
Bernie