I'm having a tough time getting it dialed to my liking.
I tend to keep the saturation knob halfway, but I have noticed the same you did, it gets way boxy with it up higher. I need to try that high shelf trick, where do you usually start it? 5k? 8k?
Another thing I noticed is that the presence knob sucks out the bass and mids when it is cranked all the way up. I think it'd be more useful if it just added presence, but that just my opinion.