how did you make out?  i'm not using the boss pedal.  i've got a momentary normally closed pedal.  it's been 2 weeks and i still can't figure out how to make this work.  i'm using an ernie ball vp jr. pedal for my expression pedal.  i've been using it successfully by itself for quite a while, but ever since trying to use it w/an external tap-tempo it's been a mess.  i use the expression pedal 90% of the time for controlling the mix of my delay presets.  all i want to do is have the external aux pedal be able to control tap-tempo commands that way i can have the H9's tap switch dedicated to scrolling presets.  here's what happens-  i do all my mappings but as soon as both pedals (EXP and Tap) are plugged in SIMULTANEOUSLY, their functions stop.  to be clear- if i unplug the expression pedal, my external tap tempo pedal works, but as soon as i plug in the expression pedal i lose them both.  conversely, if i plug in just the expression pedal, it works until i plug in the tap tempo switch.

my H9 is running on the most recent version, i have the expression jack set to "both", i have the tap tempo switch set to Sw2 (ring).  the expression pedal value is set to Sw1 (Tip).  my cable is a male TRS that turns into 2 female mono jacks that i connect to the expression & tap pedals via short male-to-male patch cables.  

not sure if it's worth mentioning but when i get the tap tempo working by itself, when i tap it, it visually moves the "wet mix" knob through it's range within the split second that the switch is engaged/disengaged.  this is the range that is assigned to the expression pedal.  i'm not sure if it's just a normal glitch, or maybe it gives a clue to solving this puzzle so i figured i'd mention it.

  i stumped and totally frustrated.  can anyone tell me what i'm doing wrong here?  thanks