Just scroll the specs chart at the bottom. Smallest sail for IS97 is 5.5 indeed. I would use a 30/32cm fin as recommended. Add a 35/37 cm if you go for the NCX 7mē. You can check on http://www.select-hydrofoils.com/en/...ed-slalom-race
for more details. Of course you won't get the very best from iSonic's with freeride sails but you probably know that already. Alternatively you may consider the Futura's 93/101 or the Fanatic Ray 100 which would suit no-cam sails better.