What are u trying to achieve with an other voice?
How are u going to play the voice? What kind of modulation u intend to use?
Squeezing another voice in 28 hp is a challenge imho.
Maybe something like oxi coral if u are willing to use midi.
Wouldn't u be better of getting some more modulation, fiters, saturation, folders and/or effects?
I'd start with that to complement the M32.
Later u could add a new voice and put the M32 back in its own skiff.