From what I am seeing...
The array for monstersquad was/has been/can be 32 rows or 0-31. Not sure if there is any real limit here.
The WaveMask values are typically not going above row 26 or so.
Reference the KF.ini:
Waves[15]=(WaveMask=125892608, is 111100000001111100000000000 which is only covering 27 rows, but that is wave 16 since it starts at 0 and not likely seen much unless sandbox.
So then... Wave 10 the standard last round for a long game:
Waves[9]=(WaveMask=39840217, is 10010111111110100111011001 which is only covering 26 rows which at this time matches the number of monstersquad rows defined in the KF.ini.
So that is to say Massacrer you only need to recalculate the WaveMasks if you are adding rows.
Just changing the existing 26 entries will spawn what you change.