... I am refering to the PYS rating given to yachts like the Contessa 32, Sonata etc. (not sure of the official description)

I have been told that these handicaps are set under class rules which would include class rules sails.

If this is correct, should a boat that raced in an open event or in a local club series with different (ie better) sails have a different handicap rating? And how would this be worked out - using a dacron to carbon/kevlar conversion as an example?