I have the Chili Red mute, and the low register without the stems in is indeed non-existent. But! Using the stems gives you many different sounds and gives you the low register back. I ended up lining the shortest tube's interior with 3mm of rubber foam from a hobby shop. This gives it a better low range and some buzz, like jazz noir muted trumpet. You pointed out that the regular Ullven harmon was tricky to hold, but that's the best part about the red one -- it stays in the bell and is nearly flush with it. Never seen a harmon mute like that before! It's the best mute, along with the triple straight plate one.
