Tempo markings placement for trio music

[Rachel Green]

Hi,
For trios, I would like all the tempo markings to occur both above all parts 
(as seen above the flute in the example below) but also right above the harp 
part. When I add a tempo marking to the harp part, it places it above the flute 
part, but when I add a regular markup to the harp part, the placement is not 
correct (too far right). Any ideas how to have tempo markings in both locations 
without manually adjusting the placement of each markup in the harp part?
Best,
Rachel



\version "2.19.80"

\language "english"
#(set-global-staff-size 18)

Markings = {
\tempo "Adagio"
s1
}


Flute = \relative c''
  {
    \clef treble
  \key a \major
  r1 |
  r1 |
   }

Viola = \relative c'
  {
  \key a \major
  \clef C
  r1
  fs4
  }


Treble = \relative c'
  {
   \clef treble
    \time 4/4
  \key a \major
  r8^\markup \bold "Adagio"
  }

 Bass = \relative c'
  {
    \clef bass
  \key a \major
  f4
  }


\score {
  <<

 \new Staff
 \with {
  instrumentName = #"Flute "
}
        { \Flute }

   \new Staff
      \with {
  instrumentName = #"Viola"
}
      { \Viola }

      \new GrandStaff
 \with {
  instrumentName = #"Harp"
}
  <<
  \new Staff = spacings \with {
        \override VerticalAxisGroup.remove-empty = ##t
        \override VerticalAxisGroup.remove-first = ##t }
        {
          \Markings
        }
  \new Staff { \Treble }
 \new Staff { \Bass }
  >>
>>
}