system-count forced in the middle of a movement?

[Kieren MacMillan]

Hi all,

Can anyone think of a way to (easily/automagically) force a desired  
system-count within a certain section of a score, without resorting  
to manual breaks?

For example, let's say in the middle of my string quartet I have a  
fugal section (not a separate movement!) that I think fits nicely on  
9 systems -- I would love to force Lilypond to set that section  
according to the fixed system count, but use automatic spacing to  
flow the rest of the movement (i.e., before and after the section in  
question) around that 9-system chunk.

Any hints/ideas would be greatly appreciated.
Kieren.