Perhaps there is an answer within the paywalled article, but I would suspect that it's an "easy in one direction but hard in reverse" problem used in cryptography e.g. it's hard to find prime numbers that multiply together to give a number X, but easy to multiply them (and get X) once you know them.

Caveats: This is from memory, and I'm not a political scientist, I'm an urban planner. I do plan on putting together "alternative" constituency boundaries at some point, eventually.

Notably, this kind of positive gerrymandering is *already a constitutional requirement*, but it appears (to my eyes) that the requirement to preserve county boundaries where possible is given higher priority – I think this is an unfair approach that punishes small/niche parties.

Long & short of it, I think, if possible, urban/suburban/commuter/rural areas should be grouped together where possible.

I also think we should put less weight on county boundaries (while still attempting to preserve them where possible) and more on demographics and physical geography – more homogeneous constituencies could also increase proportionality in my understanding.

I personally think it would be a very good idea to shift the window of acceptable constituency sizes from 3-5 to 4-6.

Was in north Cork over the weekend, and every FG poster I saw had Harris. (They were also extremely dated looking, but that's besides the point).

Meanwhile, every FG poster near me (on the border between Dublin Bay North and Dublin Central) has candidate photos.