Help with vsize and letter sized paper

[Carl McTague]

Dear Lilypond Hackers,

I'm having trouble producing output for letter sized paper; the output
consistently crosses above the top margin.  I begin my .ly file with

papersize = "letter"
\include "paper20.ly"

As an experiment, I edited the values of hsize and vsize in
ly/letter.ly to much smaller values (e.g. 4.5 \in).  Alterations to
hsize are realized, but not to vsize.  Any suggestions?

Sincerely,
  Carl McTague