Hi Gunnar Jonny
If I understand you correctly, you did not get to set up the EXP-2 as volume control for right hand sounds on the PA4X. I don't know anything about the PA5X but it might be similar to the 4X. This is how I do it on 4X. First go to Global - Menu - Controllers - Foot - Choose keyboard Expression - Exit. Then go to Menu - Keyboard Ensemble - tick off which sound you want the EXP-2 to control the volume on. I use the EXP-2 to control volume, E.G a string over a piano sound etc. EXP-2 must be connected to Assignable on the back. Don't know if it was helpful. Let me know how you like your 5X.
skude