I use a "insert" cable (TRS -> 2-TS) coupled (with a stereo TRS coupler) to my EV-5. I plug in the "tip" TS cable into my Helix (and the "ring" TS cable end is not plugged in). It works great!
(I'm using the "insert" cable to bypass the ring connectionâ€”I could rewire the pedal so it is TS only).
If I plug the pedal in normally, the volume (or other parameter) works correctly from "heel down" to mid-pedal. Then the volume (parameter) start to decrease until it is off at "toe down". It's an interesting effect, but I don't want that behavior. I just use my adapter "system" instead of rewiring the pedal.