RE: ISONIC light sailor
I think you could be quite competitive with 2 iSonics.
I am 180cm, 70 kg, and I am able to plane with iS122/7.6 TR2 sail in 11 knots of wind, so you should be able to use iSonic 122 in all winds except Formula conditions and races. If you put an 8.0 or 8.5 m^2 race sail on it you shoould plane in 10 knots or less. I don't agree with o2bnme about your need for a 145.
On the smaller size, you could look at the 101 or the 87. When you get to be overpowered with a 6.6 on the 122, at your weight you could put the same sail on the 87 and be ripping.
So in summary, with two boards I believe you should be able to compete in races in 10/11knots to 25/30 knots of wind with two iSonics.