Shifting Stones triangular area between them

The shifting stones triangular area between them… is it measured from center to center, or outside of the bases?

Stone bases

If all three Shifting Stone models in this unit are in play, place one friendly Faction model whose base is within the triangular area between them anywhere completely within 8 inches of its current location. The placed model must forfeit its normal Movement after being placed this turn. A model can be placed only once per turn as a result of Teleportation.

The second illustration, with the “triangle” drawn around them, is correct.

Source: 12+ years of prior editions’ precedent.

Link: lolwut


And confirmed by more as duke says: