automatic beaming within tuplets

[Vaclav Smilauer]

Hello,

I am unable to find the right duration fraction for autoBeamSettings so 
that it would work in triplets. (end * * * *) works fine, but that is 
not what I want as it affects everything. Pasted example shows what I 
mean; I want all the c's beamed with two beams, not four.
Thanks for help. Vaclav. (LilyPond 2.1.0)

\score {
 \notes {
   \relative c' {
     \property Voice.autoBeamSettings \override #'(end 1 8 * *) = 
#(ly:make-moment 1 2)
     \times 2/3 { c'8 c c c c c c c c c c c} d d d d d d d d
   }
 }
}