Comment #21 on issue 1015 by [email protected]: doc line width
http://code.google.com/p/lilypond/issues/detail?id=1015
huh? I'm not talking about snippets with instruments. I'm talking about
comment 0 of this issue, namely "Investigate, and produce a good,
definitive, line-width.".
...
ok, on second thought I admit that the above quote doesn't imply that
the "good, definitive, line-width" should be the default behaviour. So if
you want, I suppose you could close this issue and open a new issue
for "make the definitive line-width the default behaviour". I think it
makes slightly more sense to solve that as part of this issue 1015, but if
you want a separate issue number then I'm fine with that.
Bottom line: you've identified 15.5cm as the best line-width, but
lilypond-book does not produce images with that line-width by default.