Tempo Heading Alignment

[Will Oram]

Consider the example:

%%%

\version "2.10.0"

tempo = {
        \mark \markup { \bigger\bold {Andante.}}
}

\score {
        <<
        \override Score.RehearsalMark #'break-align-symbol = #'time-signature
        \new StaffGroup <<
                \new Staff <<
   			\override Score.RehearsalMark #'break-align-symbol = #'time- 
signature
                        \tempo
                        \new Voice { \VoiceA }
                >>
                
                %%% more instruments here...
        >> % end StaffGroup
        
        \new StaffGroup <<
                \new Staff \with { \consists "Mark_engraver" } <<
    	    		\override GrandStaff.RehearsalMark #'break-align-symbol =  
#'time-signature
                        \tempo
                        \new Voice { \VoiceB }
                >>

                %%% more instruments here...
        >>
        >>        

\layout {
        \context { \RemoveEmptyStaffContext }
        \context { \GrandStaff \consists "Instrument_name_engraver" }
}
}

%%%

The result is 'Andante' posted along the time signature above VoiceA  
(as expected and desired), but 'Andante' along the clef above VoiceB.  
I've tried messing with \override Score.RehearsalMark in various  
ways: moving Score.RehearsalMark to different spots (no change),  
adding it to both voices as Staff.RehearsalMark (no change), moving  
\with {} to \StaffGroup (pushes second 'Andante' to the top).

Is there another way to make staves with Mark_engraver added follow  
tempi alignments?

Yours &c.,

the morning lets you live
but not sleeping is too hard
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----------------------------------------------------------
                       _   |  WILL ORAM
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             & vCards / \  |
                           |  AIM spamguy21
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