Incipit alignment

[Martin Baker]

Hello. Does anyone have a solution to the ugly alignment of the part names / 
incipit in the attached screenshot? I would like the part names to be 
left-aligned and the incipits to be of equal width and aligned. I’ve pasted 
some relevant bits of the code I’m using below. Adding some spaces next to 
Cantus in \set Staff.instrumentName = “Cantus” makes some difference, but it 
doesn’t provide the elegant solution I would like. Thanks, M

\version “2.22.2"
\language “English"
incipitwidth = 5

incipitCantus = \markup {
        \score
                {
                        {
                        \set Staff.instrumentName = "Cantus"
                        \override NoteHead.style = #'neomensural
                        \override Rest.style = #'neomensural
                        \override Staff.TimeSignature.style = #'neomensural
                        \cadenzaOn
                        \clef "petrucci-c1"
                        \key f \major
                        \time 4/4
                        d''1
                        }
                \layout {
                        line-width=\incipitwidth
                        indent = 0
                        }
                        }
                }


In the score block
        \set Staff.instrumentName = \incipitCantus

In the paper block
        indent = 3.5\cm