I don't think you're going to be able to put the H9 in parallel with another stompbox like this. The H9 being a digital effects unit is going to slightly delay the signal as it goes through the H9. If you try to mix it's output signal with the original signal (or some modified version of it) coming from a parallel path, you're going to get phase cancellation which is going to cause volume drops:
http://www.sageaudio.com/blog/pre-mastering-tips/phase-cancellation.php
