I am controlling a line 6 M13 with the Ground Control Pro. Everything is working fine except for the expression pedal. I am using a Roland EV5 expression pedal with the GCP. When I use the expression pedal, the effects on the M13 do not respond in real time, and it can take over a second for the M13 to catch up once I stop using the pedal. If I go into the edit mode on the GCP, I can see the numbers changing in real time as I use the pedal, so there is no lag up to that point anyway. I have controlled the M13 before with the expression pedal on a boss GT-6, and have had absolutely no problems.