Maintaining font-size regardless of staff-size

[David Sumbler]

At the moment I define variables for formatting title, composer etc. at
the start of a score separately for each staff-size that I use.

A simple question: is there a way of getting the same layout and font-
sizes for the opening headings of, say, a part with 20-point staves and
a full score with 16-point staves without having to define the layout
twice?

Using \abs-fontsize does not work, because the horizontal spacing is
still affected by the global staff size.

David