Increasing zombie spawns in A20

[Sjustus548]

In every previous Alpha build I've always increased the zombie spawn numbers and frequency to make the game more challenging but wondering if that is possible/needed still.  Can we still change the values in the spawning file to increase the spawn numbers or have they changed it so that is no longer possible?  Do you feel like the game still needs the higher zombie spawns to increase the challenge?  We are getting ready to make a new world soon and trying to decide if we need to make the usual changes, we would rather start with more zombies than have to increase them later.  Any help would be greatly appreciated.