I am 72 kilos and have the iSonic 110 with a H2 8.2 and a SCS 7.0. The board is a lightwind machine for me. It takes a little technique to get it going in the lightest gust, but once up planing it goes through lulls with ease. The speed makes me often believe there is enough wind to plane through every jibe and in the lightest wind I always get surprised about how light the wind is when I turn right down wind and come to a stop. A little more wind and the board screams through the jibes full planing with ease.
With the 7.0 the board feels like a speed board. I am amazed how good it works being so big.
At 140 pounds I can not think that you need anything bigger than a 110.
Only thing is that I do not sail in fresh waters, but I weight almost 20 pounds more than you.