longboard fins (single-fin)

hi…could please anyone give me advice choosing my longboard fin? I’m 173 cm tall and my weight is 65 kg. board dimensions are 8’10, 22.4’, 65.6 l, round-pin tail, classic shape. style: slow an smooth, walking on board (trying not to fall
, noserides!
I recently tried a friends “koalition 7.5 tropical leaves” and loved it. but investigating I learned that a board like mine would need the 8.5 version (looks that it has not too much more area being shaped a little different…am I right?).
So, which one should I choose, I’m afraid the board would get stiffer with a longer fin but honestly i’m learning that “fin-comprehension” is a science lots more difficult that I thought.
thanks for helping!!


I recently tried a friends “koalition 7.5 tropical leaves” and loved it. but investigating I learned that a board like mine would need the 8.5 version (looks that it has not too much more area being shaped a little different…am I right?).
So, which one should I choose, I’m afraid the board would get stiffer with a longer fin but honestly i’m learning that “fin-comprehension” is a science lots more difficult that I thought.

thanks for helping!!
