Which year your iSonic 133 ?
If 2007, don't go bigger than 52-54 cm (54 cm OFO).
If 2008, a 56 cm fin might be OK (57 cm OFO).
BTW, Rémi is using a 52 cm max fin on both iSonic 133 with CR2 10 m2 sail, mainly because too large a fin is slow for top speed slalom racing.
Last edited by Jean-Marc; 3rd September 2007 at 01:49 PM.