Thanks Sean for the answer.
What I understand is that there is no need for large cutdown fins nowadays because new fins give a lot of power.
So 70-71 ones propably work as light to medium winds
And 68-69 fins work in medium-high winds
Please correct me if i am wrong,as I am just doing assumptions.
I am basicly looking for a 14-25 knot fin for my vapor board
but I don't want to get stuck with a fin that work in 20knots and above as the old days 68 fins.