Removing Stems

[Br. Samuel Springuel]

I'm typesetting some chant and thus need notes without stems.  Based on 
my reading of the documentation there should be two ways to do this: 
make the stems invisible or remove the stem engraver.

I've been able to make the first option sort-of-work as in the following 
snippet:

\version "2.18.2"
\language "english"

\new Staff \with {
        \remove "Time_signature_engraver"
}
\relative c' {
        \key f \major
        \set Score.timing = ##f
        \override Staff.Stem #'transparent = ##t
        \relative c'' { c bflat a g--( a bflat g ) g-- \bar "||"
        }
}


However, as you can see, the existence of the stems is still being 
accounted for in the placement of the slur, something I don't want.

This makes me think that I should be better off with the second option, 
but I can't seem to make it work.  I tried the following without success:

\version "2.18.2"
\language "english"

\new Staff \with {
        \remove "Time_signature_engraver"
        \remove "Stem_engraver"
}
\relative c' {
        \key f \major
        \set Score.timing = ##f
        \relative c'' { c bflat a g--( a bflat g ) g-- \bar "||"
        }
}

This compiles, but the stems still show up.  What do I need to do 
differently?

--
✝✝✝✝✝✝✝✝✝✝✝✝✝✝✝✝✝✝✝✝✝✝✝✝✝
Br. Samuel, OSB
(R. Padraic Springuel)

PAX ☧ ΧΡΙΣΤΟΣ