For a 2 boards quiver with your 70kg, I'd go iSonic 86 Slim (5.5/6.0/6.6) and keep the iSonic 111 (6.6/7.3/8.0): plenty wide with 8.0 max sail for your weight (planing as of 10/11 knots).
The iSonic 122 + 8.0 sail quiver is perfect for 85+ kg racer. I don't gain nothing in early planing between iSonic 111W68/122W75/133W85 with a 8.2 m2 racing sail + 48 cm fin combo and my 65 kg. For my light weight, the limiting factor in earliest planing is clearly sail + fin size, but not much hull width (69-85 cm width) or volume (102-170 L; the iSonic 101W64 + 8.2 m2 sail + 44 cm fin combo clearly needs a tad more wind to start and sustain the planing as of 10 knots of wind). For a medium or heavy weight, this is a different story of course...
Last edited by Jean-Marc; 5th November 2009 at 06:15 AM.