Trigger directive based on child page scroll?

Hi. New to Ionic. Trying to achieve the following, and could use direction.

V3, using Lazy load modules.

I have an “elastic header” directive that attaches to ion-header, and upon content scroll, via this.content.ionScroll.subscribe, does a nice job of hiding the header (on scroll of course).

My dilemma now is that I have TABS - that contain three individual Contents (that live in their own pages) depending on tab selected.

How can my header directive Access the scroll event firing from the child contents, so I can pass this pages specfic content into my elastic header directive friend?