two-pass line breaking

[Basil Crow]

Dear list,

Suppose I have a .ly file with Score.timing set to false and no line  
breaks (that is, everything is typeset on one line):

\relative c'
{
\set Score.timing = ##f
f4 g a b
f4 g a b
f4 g a b
f4 g a b
f4 g a b
f4 g a b
f4 g a b
f4 g a b
f4 g a b
f4 g a b
f4 g a b
f4 g a b
}

Now suppose I have the following preprocessed line breaks:

tweaks = {
\break
\skip 1*4/1
\break
\skip 1*4/1
\break
\skip 1*4/1
\break
}

How can I integrated these breaks into the score?

Basil