changing staffgroup-staff-spacing

[Stefan Thomas]

Dear community,
I thought it would be possible to change the staffgroup-staff-spacing in the middle of a piece.
Unfortunately, it doesn't work.
How can I avoid the collision in bar 2 withoud increasing the staffgroup-staff-spacing generally?
Here is my example:

\version "2.14.1"

primoA = {
   \override PianoStaff.StaffGrouper #'staffgroup-staff-spacing #'basic-distance = #8 % these distances are good for the first line!
      \override PianoStaff.StaffGrouper #'staffgroup-staff-spacing #'minimum-distance = #4
  R1
  \override PianoStaff.StaffGrouper #'staffgroup-staff-spacing #'basic-distance = #35 % doesn't do anything
  \override PianoStaff.StaffGrouper #'staffgroup-staff-spacing #'minimum-distance = #35 % doesn't do anything
  \override PianoStaff.StaffGrouper #'staffgroup-staff-spacing #'padding = #35 % doesn't do anything
 R1*2
}
primoB = { 
  \clef bass
  \set Staff.pedalSustainStyle = #'mixed 
  
  c1 \break
  
  \ottava #-1 
  r4  dis,, 2 -\ppp \startTrillSpan \sustainOn  ~ dis,, 8. d,, 32 \stopTrillSpan  dis,,  | %klavier eins links 55
                \times 4/5 { f,, 32 ( \< e,, fis,, f,, g,, -\mp ) \sustainOff } r8 \ottava #0   r4 r2
}
secondoA = {
 \repeat "unfold" 2 {  <d'' g'' cis'''>1} R1
}
secondoB = { \clef bass R1 \ottava #-1 
  dis,, 4.\startTrillSpan \times 4/5 { d,,! 32 \stopTrillSpan  \< ( dis,, f,, e,, fis,, -\p ) }r2
}
\score {
  <<
    \new PianoStaff 
    << \new Staff  \primoA
      \new Staff \primoB >>
    
    \new PianoStaff
    << \new Staff  \secondoA
      \new Staff \secondoB >>
      >>
  
}