In other synths I often use a negative detune the main or upper oscillator to make sounds "darker" by narrowing the octave between the oscillators instead of spreading it. This is especially nice when the lowest osc (osc3/sub) stays in tune to no produce too juch mud in the bass.
It would be nice if there was a negative detune available for OSC1 or a switch to allow changing the detune of OSC2 to negative.