I know that I can get a freeride board planing with a 8.5 m2 from 10 knots with heavy pumping. But I find that the difference between 8 and 10 knots is huge. In this wind range every knot counts.
And there is still the issue of going upwind of course which will be hard with this equipment. No, I prefer definitely formula equipment in these conditions. It offers me a more relaxed ride, despite the heavier gear.
It remains an interestic topic, though.