Anyone know how to make this modification?

I managed to get it so Piers extend Harbour area but it doesn't work for all islands for some reason.

By "Extend" I mean that you can build even further out than the default radius.

There is a mod on Nexus that supposedly does this but apparently it doesn't work for anybody. I managed to get it working a completely different way but it's just not 100% consistent. Works fine laterally but only some of my harbours can be extended vertically.

My only guess is there are water tiles assigned to a certain influence that can't used as harbour area. That or there is some hidden anchor point from the center of the island that denotes maximum vertically distance.

Pretty sure the reason for this is that valid harbour regions differ between islands. Not just that but certain island adjacency as a result of map generation can hinder harbour radius.

Some island configurations seem to encroach or overlap each other. Would probably need to modify both the island models and coordinates.