Cairn and Zephyr suppression radius

Currently playing Online only, so cannot comment on Offline mode.
I've run into a "bug" where aggro NPCs spawn near / wander into and destroy my respite estate. It can be quite devastating to see a wild hog busting through my door, or a pack of wolves chewing through my log barricades.
Current workaround is to build a cairnhenge around the house (a ring of suppression objects, sometimes multiple concentric rings). While this is ok as a workaround, I currently have no idea what the suppression range is for the cairn and zephyr objects. As a result, I could have gaps in coverage, or an unnecessary density of cairns.

Feature request: Have a visible outline on placement for cairns and zephyr points to show the suppression effect range. This will help determine placement without leaving the realm cluttered with extra objects.

Alternate request: Find a better way of suppressing spawn of aggressive mobs near a respite estate.