I use the "Low and High Cut" in an unswitched block in my bass presets, usually just a low cut at around 40 Hz.
So far I have one in every preset at the end of the chain.
Seems to work good, hope this helps.
Before the 2.82 update I could never get HX Edit to work with the HXFX on Windows 7
(it would always say "no device connected") and I tried everything after every update.
But with version 2.82 it's now working great!
I'm not sure what you did? But I just wanted to say Thank You to the line 6 people!!!!!