Thanks, Peter! Works a treat for me. I've thought about trying one of those rotary dealies, I'm familiar. I picked up an older Visual Volume for ~$40 and it's been working well. A bit more sensitive than I'd prefer but I can roll it off at the end of a tune if I want and then visually get it right back in the ballpark (with the LED indicators) without playing.
I run XLR out to a phantom power blocker >FOH. 1/4" out to an active volume pedal and then into my powered monitor. It allows me to control my stage volume independent of FOH, while keeping the HX expression pedal free for effects. Bigger bonus for me is that this way I don't have to kneel to change my stage volume. I use a powered wedge behind the Helix so that the stage volume going toward the audience is mostly unaffected by my changes.