When I played with mouthpiece pressure, each note was clearly separated from it's neighbours by the different attack, tension and force required and that gave me a great sense of security and confidence knowing that I could play around with note shapes and dynamics a fair bit without risk of losing my grip on the note itself.
Now that I am trying to play without appreciable mouthpiece pressure, my lips are less tense, there's a thicker contact area between the lips (to form Pop's 'aperture tunnel'), but also I'm finding that the notes feel much, much closer together. The difference in effort between bottom of stave and top of stave is so ridiculously minute (slight lift of the tongue or whatever) that I'm finding some notes difficult to find at all. Did you encounter something like this when you first started with Pop's methods?
Oh dear. Too late