Hi I am also researching the Shannon Family in county Cavan. I have the Microfilm of the Index to Tithe Applotment Books from the LDS Library. It shows Shannon Families in only THREE Parishes in Cavan at the time the Tithe names were recorded [1828-1833]
DRUMGOON PARISH which overlaps Tullygarvey & Clankee Baronies and includes COOTEHILL
KILLKERE PARISH which overlaps upper Loughtee & Castlerahan Baronies
Since there are so few Shannon families at that time we may be looking for the same family.
My GrGrGrandmother CATHERINE SHANNON born about 1805 County Cavan Married James Fitzpatrick about 1830 He was also born in Cavan