longer hshortairpins for the whole score

[Stefan Thomas]

Dear lilypond-users,
I found out (with the help of the manual), that with the following tweak I can get longer hairpins.
\version "2.11.49"
\relative     { \override Voice.Hairpin #'minimum-length = #10 \time 3/4 e 4 \p\< e \ff e  }
But how can I change it for the whole score? Is it possible to write it in the layout-block?
Thanks for helping,
Stefan