dynamics in \parallelMusic

[linux]

Hello,

I mainly write music for the piano.

In the following snippet:
 
\header {
  title = "dynamics in parallelMusic"
  composer = "me"
 
}
\version "2.16.2"
{
  \parallelMusic #'(righthand lefthand){
    %bar1
    d''2\mp b'2|
    d'2 g'2|

     }
  \new PianoStaff<<
    \new Staff << \righthand >>
    \new Staff << \lefthand >>
  >>
}


the dynamics appear too close to the upper staff.

How can I make the dynamics appear in the middle between the staffs?

I attached the test.ly file...

Thank you for your help...

Gabriel

test.ly
Description: Text document