Partcombine - appear as one set of notes when the same?

[Garrett Fitzgerald]

I'm working on transcribing Sousa's "Fairest of the Fair" for Mutopia.
I just got to the Oboe part, and hit a roadblock. The Oboe part is
actually Oboe 1 and Oboe2 printed on the same staff, with only one set
of notes printing when they're playing together. Here's the first of
the sections where this takes place.
-----oboe.ly starts-----
\version "2.11.63"

oboeOne = \relative c'' {
  \clef treble
  \key ees \major

  \repeat percent 2 { g'4 aes } | g4. f8 | ees8 r ees,4->(\mf |
  \repeat volta 2 { d8 f d4~ | d8 d16( ees f8) ees16( f |
                    g8) bes g4~ | g8 g16( aes bes8) a16( bes |
                    c8) bes c4~ | c8 bes16( c d8) c16( d |
                    ees8) ees16( f g8) g16( f | ees8) bes g ees |
                    d8 f d4~ | d8 d16( ees f8) ees16( f |
                    g8) bes g4~ | g8 g16( aes bes8) a16( bes) |
                    \repeat percent 2 {\acciaccatura d8 c8 b c4 | }
                    \acciaccatura d8 c8 b c c | d8 r aes'4( |
                    g4)_\markup {\italic "giocoso"} aes( | g4 aes |
                    g4. f8 | ees2 | \repeat percent 2 {g4 aes | }
                    g4.) f8 |
                  }
  \alternative { { ees8 r ees,4 } { ees'8 r ees,4 } }
}

oboeTwo = \relative c'' {
  \clef treble
  \key ees \major

  \repeat percent 2 {bes4 c} | bes4. aes8 | g8 r ees4->\mf
  \repeat volta 2 { d8 f d4~ | d8 d16( ees f8) ees16( f |
                    g8) bes g4~ | g8 g16( aes bes8) a16( bes |
                    c8) bes c4~ | c8 bes16( c d8) c16( d |
                    ees8) ees16( f g8) g16( f | ees8) bes g ees |
                    d8 f d4~ | d8 d16( ees f8) ees16( f |
                    g8) bes g4~ | g8 g16( aes bes8) a16( bes) |
                    \repeat percent 2 {\acciaccatura d8 c8 b c4 | }
                    \acciaccatura d8 c8 b c c | d8 r bes4~ |
                    bes4 c( | bes4 c
                    bes4. aes8 | g2 | \repeat percent 2 {bes4 c | }
                    bes4.) aes8 |
                  }
  \alternative { { g8 r ees4 } { g8 r ees4\p } }
}

\score {
  \new Staff {
    <<
      \clef treble
      \time 2/4

      \partcombine
      \oboeOne
      \oboeTwo
    >>
  }
}
-----oboe.ly ends-----
Partcombine here gives me two sets of stems for each note. I'd like it
to look like the original, which you can see at
http://lcweb2.loc.gov/diglib/ihas/loc.natlib.sousa.200028144/enlarge.html?page=3&section=ALLPARTS&size=640.
Is there a relatively painless way to do this? Or should I just grit
my teeth and take the extra stems? Thanks.