rests position in otherwise empty measure.txt

[Bill Mooney]

I am preparing a score for an SATB choir with Organ accompaniment.

The S/A parts and the T/B parts are on two staves (defined with the
"\new ChoirStaff" command) , with the organ on a 'piano' staff below.
(see the \score definition below

The composition begins with two bars of rest for the choir while the
organ plays the introduction.
I am using R1 to put full bar rests in the choir parts.
Can anyone explain how I can get the rests to print on the D and G lines
(treble clef) and the F and B lines (Bass clef) They are defaulting to
F and E, and A and G, respectively (as in the attached png file)
[ie they printing two staff lines either side of the centre line -
I would like them to go one staff line either side]
r2 and r4 rests seem to exhibit similar behaviour, which I would like to
alter as well. Can this be done globally, rather than as an adjustment
for each occurrence?
I have read the manual and all the other docs I can find but I can't
find where to alter this behaviour.
Many thanks for your assistance
Bill M

\version "2.10.33"
\score {
<<
\new ChoirStaff

<<
\new Staff = women
           <<
\set Staff.instrumentName = \markup { \column {"S " "A " } }
           \new Voice =
           "sopranos" { \voiceOne << \global \sopMusic >> }
           
%\global is defined earlier and contains time and key info

           \new Voice =
           "altos" { \voiceTwo << \global \altoMusic >> }
           >>
\new Lyrics = sopranos { s1 }
\new Staff = men
           <<
\set Staff.instrumentName = \markup { \column {"T " "B " } }
           \clef bass
           \new Voice =
           "tenors" { \voiceOne <<\global \tenorMusic >> }
           \new Voice =
           "basses" { \voiceTwo <<\global \bassMusic >> }
           >>
\context Lyrics = sopranos \lyricsto sopranos \sopWords

>>

\new PianoStaff
<<
\set PianoStaff.instrumentName = " Organ  "
\new Staff = "upper"  { << \global \upper >> }
\new Staff = "lower"  { \clef bass { << \global \lower >> } }
>>
>>
\layout {
\context {
% a little smaller so lyrics can be closer to the staff
\Staff
% \override VerticalAxisGroup #minimum-Y-extent = #'(-3 . 3)

 }
  }
   }