Agree with T'bug,
It is very important to get the MSN right, especially for operators who fly both the really old A320s as well as the latest ones.
When we had the older models I remember having the 31500' limit without speedbrakes.
The company took a very practical approach and limited all aircraft to 31500' irrespective of MSN if single pack operations were planned, giving us extra fuel on the flightplan.