I hooked up a Behringer foot pedal (FCB 1010) to the iConnect4+ (along with iPad) and use one of the expression pedals for CC7 volume from about 50-127. I find that MIDI controlled volume has a greater range than using the volume antenna alone (at least to my ears). Haven’t tried the inversion technique yet. Love not having to use a computer with that iConnect4+.
Not much difference in volume from 0 to 50 or so it seems, so I use my left hand to control volume from mute to around the min pedal setting and then use the pedal to get the more expression volume to max (seems a much better p-f shaping is possible that way). Maybe a bit silly, but it seems to give me a very acceptable expressive volume range.
And the Behringer FCB has two expression pedals so I can use the other one for controlling some other parameter (and of course change expression pedals with the stomp buttons).
Also can free up my left hand completely for the ipad if I just want to use the foot pedal for volume.