Thanks for the great comparison.
I do agree about foam tips spoiling what makes the MEST so special, but I will add that if you’re willing to modify the foam tips, by cutting off maybe 1/3 of the end of the ear tip, it doesn’t affect the treble much. With the modified tips, the core will run the entire length of the ear tip. It is the foam overhang, that goes beyond the core, that primarily saps up all of the treble energy. For me, with cut Tenmak foams, a tiny bit of upper treble is dampened, making it sound more realistic to (and not as splashy sounding), plus I can insert the IEMs deep.
If you really want the ear tip to not affect the sound, cut around 1/2 of the ear tip end off, then the core essentially won‘t go past the end of the IEM nozzle, and the ear tip will only serve to seal the area between the nozzle and the walls of your ear canal.