Here are a few more, off the top of my head. TremoloPan in the 1st H9 (WIDTH set to max), to most any pitch shift algo in the 2nd one. Tremolo ‘trill’ harmonies with 1 – 4 additional pitches (parallel, or constrained to scale). Split the mono Looper up by dynamics, with some DynaVerb OMNIPRESSOR processing.
Or Sculpt‘s ‘spectral panning’ in the 1st H9, followed by Phaser BIPHAZ as TYPE, or DualVerb independent processing. Crazy-cool stuff you can do with 2 or more H9s, plus the stereo algorithms. It doesn’t matter if you start out before & after the H9s in serial / mono. All of the stereo processing takes place in the ‘parallel split’ between the H9s, and that can get summed back to mono post-H9.