I have the same amp and got the Helix a few weeks ago, hopefully to downsize from my current board.
I did get 4cm working using the preamp on the th-30. I want to use also some of the preamps in the Helix on some presets, but I am facing the same issue since the power amp does not have master volume...keeping the volume in sync between presets with helix preamps and the th30 preamp will be just a nightmare in live situations.
I am thinking of getting this pedal to control the volume on presets that use preamps on the helix, but I would have to sacrifice a loop.
I am curious about what did you finally do or if anybody knows a better solution.
