Adjust vertical space in pianostaff?

[Hans Forbrich]

Looking for some advice - 

I'm using the workaround from the examples to keep the piano pedals and
dynamics in alignment.  For some systems the piano parts are well within
the staff and there are no dynamics.  Using the workaround, these
systems appear very far apart, relative to other systems.  Therefore I'd
like to change the PianoStaff VerticalAlignment 'forced distance' at
various points in the score.

Unfortunately I can't seem to find the magic incantation to do this
(probably because I really don't understand 'translator' - still
rereading the context section of the doc.)  

Per the sample, I set the forced-distance in the translator section in
the paper block.  As far as I can tell that sets it for the entire
score.  How do I reset this at some point the the music section of the
score block? 

Thanks in advance
/Hans

(lilypond 2.1.16 on SuSE 8.2)