On point that may help with your decision -
I have an iS 111 and find that with a 7.6 race sail, I can pop up on plane as fast or faster than several of my buddies on 7.5 sails and 130 liter boards. I am much faster once powered. The point is that the iS boards with their wider tails (and with a larger fin - 42cm) perform as well or better than the larger volume boards most freeriders use in 10-20 knot winds.
I am talking about freesailing, not racing. I weight 77kg.
You should consider the iS 122.
Formula 160; iSonic 111; HiFly Move 105; Tiga 263; '85 Mistral Superlight.
Maui Sails TR 11.0; 9.2; 8.4; 7.6; 6.6; Maui Sails Switch 6.0; 5.2; Maui Sails Global 4.5; 4.0.