I spent the most time dialing that one in. I even veered from my standard approach of using identical settings on both amps to get it to sound better - used only bass from the XXL and dialed down mids on the XXL - the bass/mids mixed equally from both was creating interference and getting a stale tone. I also varied the hum setting. The lower setting on the XXL side gives the tone less of a percussive growl, which makes it a little spongier which is where it should be, but the Treadplate side needs the aggression.
You can fit a noise gate (unfortunately not a hard gate) in front - but i found it too detrimental to the tone to be worth it.
If you want some space to the tone, remove the Parametric EQ with the really high Q setting (fizz remover) and add a delay - you don't have enough DSP for a reverb.