You have access to the Heron mausoleum records is there more information there?
1796 The Cowan/Heron are not listed as Flax growers in your named areas in Co Down see
http://www.failteromhat.com/flax/down.php or in Ballylintagh in Aghadowey civil parish Co Londonderry see
http://www.failteromhat.com/flax/derry.php A later record, that is simple , incomplete in selection and material nevertheless helps others complete the tree etc is :-
1823-1837 Tithes Applotment Books based upon the work of the
Irish Genealogy Hub listing for each parish in Northern Ireland,
The relevant original books are in the
Public Record Office of Northern Ireland (PRONI) Belfast
are you connecting to everybody who appears in this
Heron, John-Townland: Ballymacashane Year: 1833-Killinchy-Down
Heron, John-Townland: Raffery Year: 1833-Killinchy-Down-
Heron, Nathl.-Townland: Raffery Year: 1833-Killinchy-Down-
Heron, Thomas-Townland: Raffery Year: 1833-Killinchy-Down-
Heron, Thomas, Jr.-Townland: Raffery Year: 1833-Killinchy-Down
Herron, James-Townland: Aughnadaragh Year: 1833-Killinchy-Down-
These townlands from a hub.
Ros Davies has a map of the townlands see
http://freepages.genealogy.rootsweb.ancestry.com/~rosdavies/MAPS/KillinchyTownlands.htmI think Aghadowey is on the northern side of Lough Neagh , about 60 miles away from Hillsborough, which in turn is about 18 miles from Killinchy. I didnt glean your connections for the names
So I am not getting anywhere, hoping others will join in