happy christmas to all, 
some other sources
Tithes Applotment Books  1823-1837 based upon the index work of the
Irish Genealogy Hub’s 
http://www.irishgenealogyhub.com/county-antrim-genealogy.php#.V9j002Woc5Q  The relevant original books are in the Public Record Office of Northern Ireland (PRONI) Belfast 
Letson, Chas.-Townland: Derrykillultagh Year: 1833-Ballinderry -Antrim
Letson, Thomas-Townland: Glenavy Year: 1826-Glenavy-Antrim
Letson, Thomas-Townland: Glenavy Year: 1834-Glenavy-Antrim
Letson, Thos.-Townland: Aghakinmoney Year: 1833-Ballinderry -Antrim
Letson, Thos.-Townland: Ballymacrevan Year: 1833-Ballinderry -Antrim
Letson, Thos.-Townland: Crewpark Year: 1833-Ballinderry -Antrim
Letson, William-Townland: Carnkilly Year: 1834-Glenavy-Antrim
Letson, Wm.-Townland: Cornkilly Year: 1826-Glenavy-Antrim
Letteson, Wm.-Townland : Fenagh Year: 1825-Portglenone-Antrim
‘Ballymena ‘ website http://
www.thebraid.com/genealogy.aspx    Letson
Old Churchyard, Ahoghill   1881   In memory of Mary Letson who depd this life 27th January 1881 aged 67 years
Griffiths valuation 1862http://www.failteromhat.com/post1845.phpLetson   , Arthur   Crew   Glenavy   Antrim 
leaving out PRONI, inc their Guide to church records, 
http://www.GenesReunited.co.uk/tree/results/letson?memberkey=0&yearofbirthrange=0&page=9several researchers with co antrim letson 
good luck