Conditional paper block

[Br. Samuel Springuel]

I have a project in which I'm including a bunch of scores into a pdf 
document using lyluatex.  In the final product, lyluatex handles 
figuring out what the appropriate line width is for the scores and 
passes that information to lilypond by adding a header to score before 
processing.

During the drafting stage, however, I compile the lilypond files 
directly in order to check my work.  The problem I'm having is that the 
default paper size for lilypond is letter paper, while the final project 
is going to be something closer to half that.  I'd like to more closely 
approximate the final product during this stage so that there are fewer 
surprises in the final in-document editing step when the final layout 
decisions are made.  Is there a way to have a paper block which sets the 
indent and linewidth but only if they have not previously been set?
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Br. Samuel, OSB
St. Anselm’s Abbey
Washington, DC
(R. Padraic Springuel)

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