vaticana staff and changing size

[Nancho Alvarez]

Hello!
I tried to make a VaticanaStaff larger, changing the font and the 
StaffSymbol. This works well for regular Staff, but in Vaticana Staff
the "stems" are not scaled. Look at the virga in the second example,
it has a very small stem compared with the notehead.

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\version "2.7.7" %windows native
\include "gregorian-init.ly"
\score{
\new VaticanaStaff {
        c' \[\virga c'\]
}
}
\score{
\new VaticanaStaff \with {fontSize = #7 \override StaffSymbol 
#'staff-space = #(magstep 7)}{
        c' \[\virga c'\]
}
}
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