hi, same position, in the rear strap i use it far back and in the front ones in the middle, all in the inner position as i like it for more freestyle than slalom. Consequently I have cutted the stock fin to 20cm... and like it. For most time freestyling than freeriding.
About your footstrap positions...also if you like more freeride-speed setup...go for outer footstrap position and use same far back in the rear position and middle in the front ones.
Then for this keep the stock fin for sails around 6.0.
I really like this board, is my favorite one, but play with it...and learn of it. I learned of it trying different positions in footstraps basicly and playing now with the fin too.