Hey-
The "neutral" position of the Width knob is fully clockwise (value of 100). This corresponds to the behavior on the H9, where the Taps alternate being panned hard left/right (provided you are using stereo out).
Btw, you shouldn't need to do any additional editing of the preset files, when going between H9 and AUv3/Desktop. Presets saved on H9 will load in the AUv3/Desktop plugin with a Width of 100.
-Tom
