17th century keyboard ornament

[Peter Van Kranenburg]

Hi all,

I'm trying to typeset some 17th century keyboard music from the Southern
Netherlands. An often used ornament is a slanted double dash through the
stem of the note (zie attached image - sorry for the bad quality).

I tried to adapt the tremolo:

-----
\version "2.8.5"

doubledash = {\once \override Voice.StemTremolo #'beam-thickness = #0.2 }

\layout { ragged-right = ##t }
\score {
\relative c'
<<
\new Staff { \time 3/4 \doubledash g'':16 g g }
\new Staff { \clef bass << { r4 \doubledash bes,,2:16 } \\ { g2~ g4 } >> }
> >
}
-----

This doesn't satisfy me. The vertical space between the dashes is too 
large. Especially when the stem is short (as is with the bes in the 
above example). I can't find a parameter to control this distance.

Can someone give me a suggestion how to typeset this ornament?

thanks in advance,
Peter van Kranenburg