I have a way of finding the infinity norm of the transfer function as follows:

1. identityMAtrix

>II:= IdentityMatrix(7);

2. find the infinity norm of H(jω)

>f:=s->MatrixNorm(C.(s*II-A)^-1 .B )

3. plot the function f, the maximum of f(s) is the infinity norm of the transfer function

>loglogplot(f,10^-5..10^-5)