Multi measure rest for non 4/4 measures

[lucifree]

Hi

I wanted to have something like that :

\set Score.skipBars = ##t
\time 12/8  r1*12/8*4 

ie the multi measure rest with a big 4 on top of it, meaning 4 12/8 
measures.

This works well for basic 4/4 time, but I don't succeed in not 4/4. Is 
there a trick to have this ?

Thanks,
L.