Dot positions in chord with overlapping voices

[Owen Lamb]

Hi all,

I'm engraving the following:

<<
  {
    \time 12/8
    g'4. ~ 8 f' e'
  }
  \\
  <c' a'>2.
>>

In order to keep the top dot and tie from colliding, I'd like the dots 
associated with the second voice to be placed on the left of the dotted 
quarter notehead. How can this be done?

N.B. My goal is also Gould's preferred way of engraving such chords; see 
p. 58: Overlapping Chords. By default, LilyPond outputs her example 
chords as she would have them "in cramped conditions":

<<
  {
    \cadenzaOn
    <f' a'>2. <e' g'>
  } \\ {
    <c' f''>2. <d' d''>
  }
>>

Thanks in advance,
Owen Lamb