This video demonstrates how panning (pan law) across A/B Split paths in Helix gives a 6dB increase in volume in the center position which is not optimum for live use with the expression pedal (or much else, for that matter).
From what I was able to determine, there is no pan law in effect at all; a 0 dB pan law gives a 6 dB boost in the center position, which is what I measured. Digital Igloo indicated that a -3 dB pan law is in use, but I didn't find that.
I really hope Line 6 will give this due consideration, and change to a more useful pan law, such as -6, which would give neither boost nor drop in volume in the center position.
https://youtu.be/nevPesfpGgM