Best option lightweight and lightwind

I am currently an int/adv windsurfer and wondering what the best option is for a lightwieght (65 kg) and light wind. I generally sail in a bay with a steady seabreeze that cosistanly blows 8-14kts with 10-12kts being avereage. I have a 10.0 sail and was initally thinking of getting a formula board however the ultrasonic seems to suit my riding style better. I was wondering with my weight, could I go with an isoinc 127 and still have a low planning threshold while having more manuverabily than the ultrasonic with the 10.0?