As a big US147 fan, I still would like to add something.
First of all, I'm not in your weight category (87kg) nor do I have experience with the Futura, but because you write that you often sail on inland lakes, I would strongly suggest he US147.
Where I surf on lakes, I always experience a lot of lulls, especially in ultra light conditions. This means that I often have to choose some downwind angles to keep on planing through lulls and regain some height when I'm on parts of the lake with better wind. A wider board with a larger fin will always help you point better and easily bring you back to your starting point, i.e. in planing mode.
With your weight and your 9.5, you will probably plane earlier than me with my 10.9.
Oh and don't underestimate the speed of the US147. It's really fast and it feels like a feather under your feet. Probably you've already checked the weight of the US147 and the Fu141. It's the same.