I've still got to clean up the cuts some more and straighten them out with a file, but it already plays worlds better in tune. I trimmed both the inner and outer tubes rather than mess with the spacer inside.
In progress:
Jordan
King 2341 with a Holton "Monster" Eb bell
Eb Frankentuba
Martin Medium Eb Helicon
If at first you don't succeed, skydiving's probably not for you.