Have you seen this report that mentions the Camerons of Islandmagee briefly, but in some depth?
https://www.midandeastantrim.gov.uk/downloads/blackhead-path-tourism-development-feasibility-study-final-report.pdf(Text copied below in reference to Port Davey - there is also a picture of Robert Cameron's farmhouse.)
"Other users of the port during the 18th and 19th Centuries were the Cameron family. Robert Cameron (1750- 1863) owned a farmhouse and large parcel of land at Bentra, which included a small limestone quarry and lime kiln. He had three sailing vessels which were used to transport wheat, beans and limestone to Portpatrick, Scotland. His son, Robert Cameron (1790- 1863) owned a schooner called Jane Campbell. Forty-seven acres of land (which included a wharf and lime kiln) in the townlands of Cloughfin and Temple-Effin, Islandmagee, were also leased by the Cameron family from Arthur, Viscount Dungannon. The lease of December 23 1823 was for a period of 31 years."
"The land at Bentra was later owned by James Long, and the land at Cloughfin and Temple-Effin was owned for many years by the Milliken family. The Hagan and Auld families who have long connections with Port Davey and the townland of Castletown are related to the Cameron family. In later years it was mainly used by the seafaring residents of Castletown, such as Captain Auld and Captain Hagan. Up until about 30 years ago rowing boats and the occasional motor boat could be seen entering and leaving the little port."
DNA testing led me to this branch of my Cameron line, as well as to the Camerons of Loudoun Hill, Ayrshire, in Scotland, going back to the 1620's. (My ancestor Thomas Cameron sailed to Charleston, South Carolina in America in 1772 from Larne.)
More on Camerons of Loudoun Hill, Ayrshire, Scotland:
http://decorateit.ca/cameron/cameronfamily_tree.htmMultiple sources in America say these Camerons were die-hard Covenanters, and the Loudoun Hill Camerons had a Thomas Cameron jailed after the Battle of Bothwell Brig in 1679.
My ancestor Thomas Cameron, born in 1730s, is likely a cousin of the Robert Cameron described above. (Recurring family names include John, James, Thomas, Robert and William.) When my ancestor Thomas arrived in America he went into business in "teaming and freighting," hauling goods from the docks of Charleston to the backcountry of South Carolina where many other new Scots-Irish arrivals settled. The description above makes it seems likely he was in the same business before, in Ireland, if his family was in the business of transporting goods to Scotland, and when he sailed in 1772 he paid his own passage, so was likely not poor (as would make sense, if his cousin was renting the lands described above).
PS - my Cameron line went on to be deeply involved in the American Revolution and Civil War, let me know if you're interested in any further information!