I run three in the FX Loop all in stereo …. Works great.

connected via midi to keep things in sync.

multiple H9's really do open up possibilities that I would not have condsidered before, as i say I use them in an FX loop, so I can treat the H9's as a single effect eg create an effect made up of different algorithms containing  band delays and reverbs etc… Then still blend in the dry path… Works great