shorten beamed stems without overriding beam-positions?

[Roland Goretzki]

Hi at all.

I'm using version 2.2.0
and want to shorten many beamed stems in a way, which allows to
transpose the whole score afterwards several times, so I cannot use e.g.
\override Beam #'positions = #'(2 . 0).

In my short example at the bottom I can't find a way to shorten the
stems enough. :-(
With \override Stem #'beamed-lengths = #'(1) there is no way.
I also made experiments with minimum-free-lengths and
extreme-minimum-free-lengths, but no result.

It seems, as if one could only make the stems longer ...
e.g. with \override Stem #'beamed-lengths = #'(7)

Can somebody help me, please?
Best Regards           Roland 

Example:
=======================================================================
\include "deutsch.ly"
\score {
  \context Staff \notes \transpose c' c' {
    \relative c'' {
      \key c \major
      << { \shiftOnn
           \override Stem #'beamed-lengths = #'(1)
           \times 2/3 { g8 h d }
           \times 2/3 { g, h d }
         }
           \\
         { c,2 }
           \\
         { e'2 }
      >>
    }
  }
}
=======================================================================