You make a good point about the 4th stage. I usually back the depth off a bit when going there as it is fuller sounding. The goal was to voice it relatively close to the 3rd stage sounds, and I could have gotten even closer by reducing the 4th stage's coupling cap value a bit. But removing some bass from the stage just killed the feel and the lead tones. Pulling the treble knob to engage the "Pull Focus" feature also will get the 4th stage noticeably leaner and tighter.
The nice thing about the 4th stage is that it can be engaged at any setting. In the lower gain "brown sound" settings, for example. It'll add some nice texture to those