weird page breaking

[Kieren Richard MacMillan]

[ Lilypond 2.8.1 ]

Hello, all --

I know it's hard to diagnose a problem without sample code, but I'm  
too deep in a large project to try to derive a minimal example, and  
I'm hoping someone can help me anyway...

I've got A.ly, B.ly, etc., and a Score.ly which \include-s all the  
others.

Because Lilypond cannot handle arbitrary page sizes, I'm using the  
\paper block (in Score.ly) to define a top-centre-aligned output on a  
tabloid sheet (to be printed duplex) which I will then trim down to  
the final dimensions (10x14):

    #(set-paper-size "11x17")
    line-width = 9\in
    bottom-margin = 4\in
    top-margin = 0.5\in
    between-title-space = 1\in
    ragged-bottom = ##t
    ragged-last-bottom = ##t

Unfortunately, I end up with the first page having only one system,  
even though there's lots of room for another system.

I've tried to add one (or both) of the following

    between-system-padding
    between-system-space

which solves the first-page problem, but leads to very weird page  
breaking on other pages -- in particular, one movement, which is a  
duet (and thus 5 or 6 systems fit on a single page), gets broken into  
pages with 2 systems per page, even though there is lots of room  
remaining at the bottom of the page.

Any help would be appreciated. I can even send someone all the files  
(off-list), if you'd like.

Thanks,
Kieren.