In our fleet Kootenay Lake, BC we had an A and a B fleet which used to be split 50%/50% with 168 (e.g J/24) being the typical A fleet boat (with a SJ24 and SJ21 that competed very well in the A Class)
Well now days we are getting some newer generation faster boats making their way to our lake but the "slow" boats seem to be around still with some new "slow" boats too. The new generation boats (some fast Rocket 22 and big AND fast: Schock 35) are about 100 PHRF (or LESS)
We will likely add a C class and hopefully have at least 6 boats in each Class. I have heard PHRF doesn't work that well when the spread gets to be over 50 or 60 points.
"The sail, the play of its pulse so like our own lives: so thin and yet so full of life, so noiseless when it labours hardest, so noisy and impatient when least effective". -- Henry David Thoreau