Spacing of chords on a chord lead sheet

[Raphael Mankin]

I have  generated a chord lead sheet for a bass player with just the 
chords on it (\chordMode, no notes). After some  fiddling I got the bar 
lines and repeats printed.

However, the chord names are mono-spaced; they are not spaced according 
to their durations. So that if, for instance, I  have {ef2 ef4:maj7 
ef4:7} then each symbol occupies the same amount of space on the line. 
The first chord does not occupy double the space of the other two.

Is there a way of getting proportional spacing?

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