WTG Ronan! What great results.

I'm not exactly sure what a halo ring is either?

I don't know if this is similar, but when Joshua was a newborn and didn't have much strength in his neck muscles, we used a tiny horseshoe shaped pillow under his head whenever he was on his back. (Change/play times etc). It held his head and neck in the midline and prevented him from spending too much time on either side, which can result in that "flat" look on the sides of the head.