  In this note we complete the discussion of minimality of symplectic fiber
sums. We find, that for fiber sums along spheres the minimality of the sum is
determined by the cases discussed by M. Usher and one additional case: If the
sum is the result of the rational blow-down of a symplectic -4-sphere in X,
then it is non-minimal if X contains a certain configuration of exceptional
spheres in relation to this -4-sphere.
