I recently traded up to a Dual-Output Expression Pedal (EP-25K) from Mission Engineering and added a fourth H9 to my pedalboard. This allows easy simultaneous sweep of parameters on two units at once without setup headaches. The 25K pot in the Mission pedal gets read correctly 0 – 100 by the H9s on the first sweep under settings>exp. pedal calibration and then stays calibrated even after power down. Two H9s swept in tandem with the expression pedal allows all kinds of powerful effects morphing with some parameters sweeping forward and others reversing from heel to toe. Many of Brock's preset pairs listed under "preset share" jump to life with the sweep of the pedal (thanks for many great ideas Brock!)
