RE: iSonic105 technical ride
I am somewhat surprised of the "consensus" to recommend huge boards for featherweights (at Ricbra's 66 kg). The iS133 is 80 cm wide, and the iS145 is almost 90 cm wide...
I would think that the law of "diminishing returns" comes into effect quite quickly. With the same sail size it ought to be more fun to have a board that planes almost at the same time, but is much more manouverable.
For a small guy it seems that a board around 70 cm (like iS115) wide would be sufficient as a lightwind racer, especially with decent pumping technique.
On the other hand, if the wind is strong enough for a 5.5 then a much smaller board would make sense. One with an optimum sail of about 5.5 and a max sail of 6.5. This ought to be not much wider than 60 cm (with a corresponding volume of about 95 liters, offering float like a barge).
My honest opinion is that the iS105 does not fit particularly well into a two board quiver for a 66 kg guy... It is too small as the biggest board, and too big as the smallest.