Did you have a go on your iSonic 58 speed + your 9.5 m2 sail ? How is it in say 15 knots wind ?
I'm a light weight at 65 kg. I've tried sometimes iSonic 53 speed + Reflex III 8.6 m2 sail + Deboichet SL4 32 cm in ± 15 knots wind or Code Red 7.7 m2 in ± 18 knots wind. Below 15 knots wind, a much wider slalom iSonic is faster (up to twice the wind speed), especially on a 500 m long course.
What is your definition of light wind speed surfing ? 15 knots of wind ? 10 knots of wind ? 7 knots of wind ?