Can you tell me the preset and parameter you are trying to control ? Please name at least one.

And, what software version are you running ? What you are trying to do should be possible.

We already make a machine with 2 engines – it is the H8000. Sadly for you, the second engine requires more dsp, which the H8000 has, and the 7600 does not, so a software upgrade will not give you what you seek.