The J24s in our area only USE class approved sails to get there 174 PHRF and get the same rating if they do a JAM race
PHRF #

we have two J105s one is and 81 and the other a 105
The boats i raced on this year with the roach problem are a Tartan 10,C&C 35 Mark I and a Tartan 372
All there race mains hit the backstay buy and easy 5"
Now is its faster BUT it is just a PITA for the crew to deal with