MAX ALT does changes after take off - it lowers.
Our FMCs default to 26.2 in CRZ CG on PERF INIT page - I modify this by adding 1.5 units to T/O MAC (we always have centre tank fuel on take-off). I also add about 5 degrees to forecast top of climb ISA dev (slightly conservative).
Any other recommendations?
A foward CG and high (ISA dev above +15) sends the MAX ALT way down.