From the HX I'm using a single Stereo 1/4" that splits to dual 1/4" into STEREO (L&R) looper inputs, generating STEREO drums etc. It's clear now that I can't use my Mono Wah pedal in this chain in any way without summing the primary HX STOMP signal to MONO, given the looper must come last.
If I place the FX BLOCK (thus the looper / wah) in the HX STOMP before any HX effects blocks, those will then effect the drums which is not desirable.