can't get more than 3 systems on first page

[Paul Scott]

Lily 11.32  With these (and many other) paper specifications for a score 
for piano and various voices I can't get more than three systems on the 
first page no matter what the font size is.  There is clearly enough 
room for another system.  This is not public domain music so I am not 
giving an example unless I get no responses.

\paper{
 #(set-paper-size "letter")
 line-width = 7.4\in
 before-title-space = 0\cm
 after-title-space = 0\cm
 ragged-bottom = ##t
 ragged-last-bottom = ##t
 between-system-space = .4\cm
 between-system-padding = .6\cm
 interscoreline = .1\cm
 top-margin = .3\cm
 bottom-margin = .3\cm
}

\layout{
 indent = 0\in
 \context { \RemoveEmptyStaffContext }
}


TIA for any ideas,

Paul Scott