As shown for the benzene stack, differences between local and cumulative GAS constraints exist, but their practical effect on the energetics is in general negligible. GASCI calculations with an excitation level n exc of 1 and 2 were performed. Higher excitation levels were not necessary as convergence is reached already for n exc = 2. As in the case of N 4 it was not possible to use disconnected spaces (n exc = 0) due to the ferromagnetic ordering.