sa 500 starlet airfoil

I'm looking for the right airfoil data for the starlet homebuilt
I would like to start first of all making a mockup of the wing to
understand difficults and may be later with the right materials
I have the drawings of the plane but I cannot understand why there is
difference
between the CYH(is it?) standard airfoil(Max Thck=11,7%) and the
plans.May be because of the hardcopy scale,infact the MAX thickness on
the drawings result to be 12,7%(circa).Unfortunately plans are not
completely dimensioned,so I should make parts copying them and I
don'like it
What can I do?
Somebody can help me?
Thanks