System spacing in a markup score

[Pierre Perol-Schneider]

Hi List,

How can I access the paper defs in a markup score?
E.g. system-system-spacing?

Example:
%%%
\version "2.20.0"

\paper {
  system-system-spacing.basic-distance = 5
}

\markup {
  \score {
    \new Staff { \repeat unfold 10  { c' d' e' f' } g' \bar "|." }
    \layout {
      system-count = 3
      line-width = 90
      \context { \Score \override BarNumber.font-size = #-4 }
      \context { \Staff \magnifyStaff #5/8 }
    }
  }
}
%%%

Tia, cheers,
Pierre