I note that sib1.png is exactly the same chord as in the Gould scan. And
it has two less dots than Gould shows. So it's not consistent with Gould.
I'm not quite sure what she's showing in that example you scanned, but I thought it was about centering the dots.
If the trim rule for Gould were "trim to the chord spaces if the dot
spaces are two or more staff spaces larger than the chord spaces", then
we'd get the Sibelius output.
If you could check what she shows for the 9th-spanned cluster chord (which Brian mentioned above) -- Brian said she shows only five dots there. So perhaps she's not self-consistent.
The current logic doesn't reflect Gould's rules at all, as it only refers
to the number of staff positions taken by the chord, not the number of
staff spaces taken by the chord. And Gould clearly considers staff spaces
to be the important metric in her rules.
I think the trouble with Gould's rules is that they're inconsistent, or could at least be interpreted in such a way. She says to use dots only on the spaces occupied by the chord, and yet says you MAY need to put a dot a space or more away from the chord.
So the challenge is to figure out a way to implement Gould's rules with
some adjustable parameter that allow us to get Sibelius's rules.
At the very least, we should be able to decide in our own scores what logic is used for dot placement :-)
Are you editing the code in dot-column.cc. or is there some Scheme code for this too?
Chris