stem lengths

[Stan Sanderson]

Lilypond 2.0.1

I've reached my limits.

In the following fragment, a clef change occurs after the first note 
(I'm transcribing an old piece and trying to keep the original stiyle). 
I've tried everything I know of to lengthen the stems so that the beam 
clears the treble clef sign. I'd imagine there is a simple answer, but 
I haven't found it (at least in an understandable form) in the 
documentation.

I'd be grateful for suggestions.

Stan

\version "2.0.1"
\include "english.ly"
\include "paper16.ly"

RH = \notes
        \relative c'' {
        \key ef\major
        \time 6/8
        c4 d8 f ef c
        }
        
LH = \notes
        \relative c {
        \key ef\major
        \time 6/8
        af8 \clef treble c' ef af ef c
        }
        
\score {
        \context PianoStaff <<
                \context Staff = "up" <<
                \clef treble
                        \context Voice = VoiceI \RH
                        >>
                \context Staff = "down" <<
                \clef bass
                        \context Voice = VoiceI \LH
                        >>
                >>


\paper {
                \translator { \RemoveEmptyStaffContext }
                raggedright = ##t
                }
}