Vertical-Spacing

[Jan-Peter Voigt]

Hello Lilypond-Users,

I am trying to set an eight-voice choral score in four staffs (SATB).  
This is working out very well and my choir-singing fellows appreciate  
the nice look of my lilypond-scores.
Right now I am compiling a collection of pieces to a book. One of  
these pieces shows up with a phenomenom, wich I do not understand:
The default-staff-size is set to 16 - that makes 3 SATB-systems. But  
there is one page with only 2 systems leaving a lot of blank space in  
the middle. I tried to tweak with VerticalAxisGroup on Staff and on  
Lyrics, but that didn't change this. If I change the default-staff- 
size to 15 or 17, the blank fields shows up on different pages. I used  
'\set stanza' to save vertical space with dynamics and some annotations.
Annotate-spacing showed up a metric wich would indeed leave space for  
3 systems on the said pages.
How else can I try to prevent this?

I hope this is not an annoying blind-eyes-newbie-question!

Have a good day.
Regards, Jan-Peter.