Increasing spacing between staves

[David Sumbler]

Is there some way of increasing or specifying the space between the 2
staves of a piano staff at a particular point in a score?

The piece I am setting has a lot of cross-staff beams, and sometimes
Lilypond does not allow enough space between the staves for a decent-
looking beam.  In those cases I would like to force a greater space
between the 2 staves just for that particular printed line of music.

I do not wish to alter the minimum staff spacing globally.  But the
particular points where extra spacing is needed may not occur at the
beginning of a line, and of course the spacing of the whole line must
be changed.

Can this be done?

David