This is definitely doable, I had used this in my rig before, and its in the user manual. I dont have my H9’s anymore but it goes something like this:
H9 #1 setup basic midi channel/XMT and add:
[XMT CC] –Transmit MIDI Continuous Control
[PDL.C15] SOURCE: expression pedal; DESTINATION: continuous controller on 15 (“standard” pedal CC)
[CTL.XMT] – MIDI Continuous Controller Transmit Enable (ON, OFF)
H9#2 must be set/configured to receive CC on same controller
[RCV CH] the same channel H9#1 transmits MIDI over
[RCV.CTL] set to EXP CC15
see User Manual p.46-48