Ros Davies website 
http://freepages.genealogy.rootsweb.ancestry.com/~rosdavies extract reads as you know
[Hamilton) Peacock LOGAN Killinchy married Jane Davidson 27 Mar 1816 at Killinchy Presbyterian Church   PR 
in the same database
perhaps a sister is
Miss Margaret LOGAN Killinchy married John Black 28 Oct 1813 at Killinchy Presbyterian Church PR
perhaps a brother is is
William LOGAN Killinchy married Agnes Hutton 23 Dec 1825 at Killinchy Presbyterian Church PR  
There is more than one 
Killinchy Presbyterian Church, however even though the first church is much older, surviving records 
start 1812, are there earlier tombstones ? or tombstones with information that go back before 1812 see ros davies website under killinchy churches
do the baptisms say for 1812 – 1830 include parents names enabling one o go back one generation.?
the 
Tithe-Applotment-Books originals are in PRONI , it is a simple listing showing the acreage of land good and poor which sometimes help connect to Griffiths valuation later proving the homestead’s earlierbexistence
Tithe-Applotment-Books 
http://www.irishgenealogyhub.com/down/tithe-applotment-books/killinchy-parish.php#.V1Ug5Feoc5QLogan, George   Townland: 
Craigaruskey Year: 1833 ie the townland immediately above Killinchy towland
Logan, James      Townland:
 Ballow Year: 1833 aka  
Balloo currently,  the immediate townland west of Killinchy townland George is there in 1863
Griffith-Valuation http://www.askaboutireland.ie/griffith-valuation has a George in 1863 in Ballymacreelly map ref 69 and 70 and in Balloo map ref 17 with 2 tenants as well.
So Craigaruskey no longer,  Ballymacreelly townland lies under Balloo.  have you looked up the maps supplied on that website ?  have you then tried the same roads on a modern google map going into satelite then view the street scene and drive around the area by shifting the view along the roads. as an exile it is a treat.
Flax growers in ireland no mention of logan in 1796 
http://www.failteromhat.com/flax/down.phpin 1783 
James Logan is the only Logan freeholder listed in killinchy, the original list is downloadable from PRONI freeholders section
PRONI also has the index entry  for 1833 only has survived for a will of a Frances logan, widow of a 
John Logan of Ravarra killinchy that is the fourth townland going westwards from Ballooin the west of the parish
what other resources might exist
Muster Rolls  see Bill Macafee for north ulster i have seen one for co down but where 
Hearth Money Rolls - Bill Macafee states The original Hearth Money Rolls were destroyed by fire in the Four Courts, Dublin in 1922. However, the Presbyterian Historical Society of Ireland had made copies of the Rolls and these were lent to PRONI in the mid-1920s for copying.
Protestant Listings 1740s they exist for Banbridge 1740s
1766 religious census Bill Macafee states In March and April 1766 Church of Ireland rectors were instructed by the government to make a return of all householders in their parishes showing their religion. Unfortunately the original returns were lost in the 1922 fire in the Four Courts, Dublin. We therefore have to rely on the transcripts of Tenison Groves
Intermarriages with killinchy families that have earlier records than 1812 etc
you may know all of this but I didnt know the boundaries to expect until I did my thing.  good luck onwards and thanks to your previous correspondents and their links.