Hallelujah! After several years of futile searching I have finally found the correct tweak to make gracenotes non-stretchable in Lilypond. Yesss!!

To celebrate this great discovery, I have regenerated all of the tunes in the Sheet music section of the site. Because of the new and improved spacing this gets me, I have also been able to reinsert a bunch of line breaks that were removed previously to make the layout suck less. Now it doesn’t suck at all!