OK, lets explore further why I've come to the conclusion of a family connection to the Francis Johnston mentioned in Griffiths.
As you pointed out, Muckros is a very small townland and there are only 2 Johnston's mentioned in Griffiths, namely John and Francis Johnston.
The earliest map I have (OS map, Edition 1907, Fermanagh Sheet No 5 - scale 880 ft to one inch surveyed in 1835 and revised in 1903) indicates that there appears to be a total of perhaps 8 collections of buildings clustered together in farm formations across the whole of the Townland.
That, along with the number of people who appear in Griffiths as being resident in Muckros at the time when Griffiths was drawn up also confirms the limited number of people involved.
From memory, Griffiths Valuation of Fermanagh was done in about 1860 and published a couple of years later.
My ancestor left Fermanagh at about that time. I say 'about' because I know he and his brother took up land in NSW and first appear on land ownership records in NSW in 1862. I strongly suspect (based on a surgeon's list from passenger records) that he and his brother arrived in NSW in 1860. I cannot 'prove' this was him and his brother as he left no written record saying which ship on which he travelled.
They were discharged from this ship to their cousin, the Irvine chap I mentioned in an earlier post, and who gives his address as being in an area of NSW where I know my ancestor and his brother were located prior to taking up land and to where the James (perhaps John) Johnston later returned. The Irvine cousin also seems to appear later on as living in the same district as where my two Johnstons first selected and settled on the land - again not a certainty given the lack of uniqueness of his name.
So, the date for his family being in Muckros at the time of Griffiths fits with the time of his leaving Fermanagh and it also fits his having 'Muckros' recorded as his home townland as given on his headstone. Francis William Johnston's DC gives the name of his parents as being Francis William and Isabella.
So hard facts (provable from available documentation) are: time of Griffiths, time of land aquisition, names of Francis William Johnston and the names of his parents and the townland he came from in Ireland.
So to sum up: unless there were at least 2 Francis William Johnstons, one of whom lived in Muckros at the time of Griffiths and who was the parent of my ancestor and then another named the same and who lived there in 1893 at the time of the death of one of those so named, and they both had a son called Francis William and they both had a wife who was called Isabella, then it is more than likely that the one mentioned in Griffiths and the one who died in 1893 is one and the same and therefore the father of my ancestor.
Not a certainty I know but certainly 'most' likely (and far more likely than many claims I see as being 'proven').
I also know that "Protestant" isn't a religion, however since my ancestor was involved once he came to NSW in the Wesleyan Methodists, the Church of England and also the Presbyterian Church, I cannot with any certainty assign to him any specific religion and certainly not C of I as there was no such thing by that name in NSW.
'Protestant' it must be until I can 'prove' his baptism (as if one can actually 'prove' anything when it comes to Irish records!) it seems most likely that his birth is recorded in Magherculmoney C of I in January 1835.
Do you have any further comments or suggestions as to where to go from here or have any further points you may wish to add about my conclusion? I would be most interested as I too am very fussy about making claims of proof or probablity where none exists and a fresh eye cast over my conclusions is always welcome.
And you didn't mention whether you have any interest in Johnstons in Muckros or indeed in any other part of Fermanagh. Are you too seeking information on Johnstons in Fermanagh?