Brownell and Young at '59 have included to their Process Design Handbook and in an example at flanges design chapter a following equation for the minimum gasket widht:

Nmin=AbSa/3.14G(2Y) ( nomenclature is well known)

This equation may have arised for an balance between bolt stress and gasket stress during seating i.e.( at least non other explanation I have find or I can imagine)

bolt area x bolt all. stress = gasket area x gasket all. stress or
AbSa=3.14GNmin(2Y)

were assumed that gasket allowable stress=2Y i.e 2xminimum gasket stress

Now, supposing you have a) spiral wound gasket Y=10000psi
b) kammprofile gasket Y=4000psi

From above equation it arises that spiral wound gasket need to be much more thinner from a kammprofile for having the same strenght.
With other words a spiral wound gasket all. stress is higher than the kammprofile's ??
But I have find in gasket manufacturer that kammprofile all.stress is 75000psi appr. 18 times bigger than Y.
So, what I must do? I must ignore Brownell Young equation or I must respect it and to try finding a kammprofile gasket with N=40mm, because this is what this equation gives ??
Also I want to note here that acc. TEMA minimum gasket widht is 1/2" for such a G values