Seeking family of Moses Culbert (1804-1860) and James John? Culbert (c. 1797-1871) of County Donegal

My immigrant ancestor, Moses Culbert, stated in his U.S. naturalization papers that he was born in "Letterkenny town."  Moses emigrated via Londonderry in 1828.  His brother, known as James Culbert here, may have been the John Culbert naturalized in 1830 in Delaware, U.S.A.  This would mean John emigrated at least 5 years before 1830.

My information on Moses can be found here:

http://culbert.one-name.net/getperson.php?personID=I00162&tree=Culbert

My information on James can be found here:

http://culbert.one-name.net/getperson.php?personID=I02078&tree=Culbert

Unfortunately, our family has no information on the family left behind in Ireland.  My research from afar has turned up no evidence of any Culberts living in Letterkenny during the late 1700 to mid-1800 time period.  So, I am supposing that this family resided in one of the surrounding parishes.  Family tradition says the family name was Culbertson in Ireland.

All of the 1796 Flax List individuals in Co. Donegal are good candidates to be related to Moses and James, but I cannot find out more information about them.  They are listed here:

http://culbert.one-name.net/showsource.php?sourceID=S2326&tree=Culbert

I hope someone can help.

Jim Culbert

McMinnville, OR, USA