Belated thanks to those who responded to my query regarding usage of PY for shorter race durations.
I think that the perception that Portsmouth was based on race durations of 100 minutes came from the older system of ratings using base 100, compared to the current system using base 1000.
I accept that the system should not be time dependent, but I suppose the race should be of sufficient duration to bring about class differences. i.e a spinnaker / trapeze boat will have to have opportunity to use these to be able to pull away from classes without these mechanisms.
regards,
Malcolm Osborne
Sedgefield, South Africa