RFX M/S Tutorial Setup 1 ( ONE)
You need two Buses wich go into a GFX Bus .
Don´t forget to set the Main output in the Buses to 000% !
This both Buses have to set on 100% in the Mixer Menu .
The output of the Preset is set to Mixer in the MultiMode Page .
You need a Stereo Preset ! 
Insert the “MixerPlugIn” in both buses.
In the first Bus we make an inverted mono Signal ( That is later our Side Signal )
For that you scroll down and go into the split modus.
Set the Pan of L and R to Center.
And set L-Phase and R-Phase to” inverted “- Default is it set to “normal “.
Let the rest of the Parameter as it is ! No EQ , no nothing .( It comes later , if you know what you do )
The second MixerPlugIn in Bus Two has the same Settings except in the “EditMod you set the ModWheel – ( or any CC ) to Wet/Dry Mix .
Know you can Scroll via ModWhl up to Side – normal Stereo – Mono .
RFX M/S Tutorial Setup 2 (TWO )
An other way i found out is because i wanted to modulate this Effect via the Preset in the Chord Page.
Here we go :
You need 3 ( three! ) buses within 3 ( three ) MixerPlugIns.
The Setting of the first MixerPlugIn in the Bus 1 is as above except let the Phase of both ( L + R ) to normal.
The second MixerPlug in bus 2 is set to locked Pan ( Stereo as it is when you load it ) and Phase normal.
The Third Mixer PlugIn in bus 3 is set like the Second exept Phase on “inverted”
Don´t forget to make a Stereo Preset wich goes via the Mixer in these three Buses. Bus 2 is set to 000%
…and sure you have to patch a source to destination “ SndAux1 “ 100 %
I took as source theCkDwhl to Lag0in and the Lag0 into SndAux 1
and i made a little Filter Sweep to get it tighter and deeper
It seems to be a little Bug in there because the mod is set to 100% but the Mixer needs 127 . ( ? )
So you don´t get a real Mono effect . But i work on it.
There are also other Routings possible . Let me know what you think.
Tipp: try to work with some Delays on the GFX Bus