Problem with acciaccatura and articulation

[Papa Eric]

Hi,

In the following code I cannot solve two problems:

-----
\version "2.11.42"

{ \voiceTwo
    d'8
    \acciaccatura {\once \override Stem #'direction = #up c'8}  d'8
    \acciaccatura {\once \override Stem #'direction = #up c'8}  d'8-.
}

\layout {
  ragged-last = ##t
}
-----

1) the first acciaccatura has a nice slur, but the second one is too low 
because it tries to be lower than the staccato dot (I suppose). How to 
tell the slur it to ignore the dot?

2) If I remove the first d'8 note, the stem direction of the d note 
becomes up, as if the \once did not work well. More complete example:

\version "2.11.42"

\new Staff
    <<
    \new Voice { \voiceOne
        f''4
    }
    \new Voice { \voiceTwo
        % here insert d'8[ to make it work (remove next "[")
        \acciaccatura {\once \override Stem #'direction = #up c'8}
        d'8[
        \acciaccatura {\once \override Stem #'direction = #up c'8}
        d'8-. ]
    }
    >>
\layout {
  ragged-last = ##t
}

Thanks for any hint (especially with the staccoto dot, which annoys me 
more in the true score!)

Eric