Originally Posted by Pelegrin
There is still a lot fun in lightwind conditions without using Formula-equipment. I sail JP SLW 154 with sails between 5.5 and 9.0. The SLW is fairly like the Ultrasonic. The SLW has a great pontential and works perfectly well with all these sail sizes. If You like reaching in 20-27 knots it is fantastic. If You like going upwind in 15-21 knots it is fantastic. If you like going downwind it is fantastic and not at all scary.
Fantastic ? Really ? This is unrealistic for a 65 kg rider. The Ultrasonic is an absolute horror with a 5.5 sail in 20-27 knots for a 65 kg rider: way too wide! Time to get real, sorry about that...
I have also an Isonic 127 since this autumn and the feeling is similar to the SLW. This is also a great board but perhaps 10.0 is a rather big sail on this board with You weight...?
If I'm correct, you weight 78 kg. This is a different story as compared to a 65 kg weight rider.
Again, I've riden the iSonic 127 with my 11 m2 sail and I've found there is no control problems in low/high wind range (i.e., 7-12 knots of wind). I'm sure a 10.0 sail will fit the bill as well. However, things start to get scary in higher wind range with say an 8.0-8.5 sail. Control problems will emerge when the board is too wide, too bulky underfoot with vatsly unnecessary balast volume. A 65 kg light weight rider simply has not enough weight to keep control of a +85 cm wide board in higher wind range because of the associated chop/swell building up. We simply have not enough leverage to keep the hammer down when the board starts to fly or tailwalk when chop hopping in higher wind. If you do, you'll need superior skills to keep da big Bertha under control in rough water at high speed, no question...
Therefore, an iSonic 127 is a good choice with a 10-11 m2 sail for a 65 kg rider as a 1 board + 1 sail quiver for light wind conditions (i.e., 7-12 knots of wind).
If you're looking for a 1 board + 2 sails quiver solution for a skilled 65 kg rider, I would rather choose the iSonic 117 wide with 8.x + 10.x sails quiver.
If weighting 78 or 87 kg, this is again a different story...