elastic space between staves

[Werner LEMBERG]

[lilypond 2.2.x]


Consider the following situation.  You have a score with three staves,
and you want two systems per page (using a quite small paper size):


        -------------------

        -------------------

        -------------------



        -------------------

        -------------------

        -------------------


The first page has title, a subtitle, etc., and should look like this:


              F o o
            blablabla

                       xxxx
        -------------------
        -------------------
        -------------------


        -------------------
        -------------------
        -------------------


As you can see, both the space between systems and the space between
staves is squeezed.  In the ASCII drawing above, the squeezing is
exaggerated, but you can see what I mean.  In TeX terms, I would like
to have e.g.

   \def\interstaffspaceskip{5mm minus 0.8mm}

so that the vertical staff space can shrink slightly without getting
bigger.  It seems to me that at least the 2.2.x series can't do that
automatically: Only the space between systems is a rubber space, but
the spacing between staves is fixed (for technical reasons).

How do you handle this in 2.3.x?


    Werner