When a modern Catholic church marriage takes place the Catholic church requires an undertaking of the Catholic partner in a religiously mixed marriage that their children will be brought up as Catholics even if the non catholic partner does not convert, as they are not required to do.
This RULE did not apply until 1907 and I am unsure what the situation was before then. So the Catholicism sort of lags a generation if you see what I mean.
Relatively speaking there were quite a few Methodists in Leitrim too I should add.
There are many Scottish names in the area North of Leitrim and they were in situ since the early 17th century. I would point out that the two main NI nationalist/catholic politicians of the past 30 years have Scottish surnames, Messrs Adams and Hume .
The Catholic Church does not co operate with Familysearch but other denominations generally take a sanguine view of Mormon retro baptism fixations and release their records on request. Northern Ireland has a rather good geneological service by the way even though Leitrim/Cavan is technically just out of their jurisdiction. Some NI CoI dioces have portions in the south meaning they may have a complete record.
Have a shufty here too.
http://www.nationalarchives.ie/genealogy/churchmap.htmlDiocese of Kilmore as it was in 1906 looks good.
http://www.ireland.anglican.org/cmsfiles/pdf/AboutUs/library/parregs.pdfMethodism was largely a Low Church Anglican schism from the late 18th century
HTH