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. You will not dip the nose! Gybing is easy and the footstance will never get Your feet tired.
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...?