I’ve tried using the POG2 like this with the filter all the way down, it’s the best so far… but yes, still muddy with chords. I even toneprinted a SubNup with 4 pre and post-EQ filters, but those lowest notes still get garbled.
OC3 is your best bet until EHX solves this once and for all (if they realise how popular a good one would be). I know they can because there are rack mounted units that can creat a single subbass note below the lowest note. With that said, one such rack unit might be your best option.