I really like John Paul Braddock's cube visualization, because it is how I have been thinking of mastering recently.  The concept of filling up the audio space which is a cube with the vertical axis representing frequency, the horizontal axis representing mid/side and depth representing volume front to rear. My visualization was only a 2D square until I saw John Paul's cube.

John Paul has a really good 'Modern Mastering' master class in the January 2015 edition of Computer Music magazine . In particular relevant in the Scope context because it focuses on software mastering.

In the magazine it shows the same cube but filled up - e.g. solid. I think this might be what you are trying to achieve - so helps to be cognizant of 'loudness' in those 3 dimensions rather than just a single gain dimension.

If you own an iPad this magazine costs less than $3 bucks per issue - an absolute steal really - considering back in hard copy days I was importing them for like $25 each !  Never has so much been available to so many for so little.

The beauty of this concept is that once embraced, it gives another perspective on the sometimes bewildering array of parameters on many mastering plug-ins.  Once you know what it is you are trying to achieve, understanding the devices becomes a little easier.

The ability to switch between listening to the mid or the side of a mix for adjustment and comparison to the full mix is an invaluable tool.