I am not researching these families just wondered if you had seen the Griffith Valuation from 1857, where 6 Fergusons lived in Ballysadare Parish and 7 Meredith's of the same Parish.
Thomas Meredith owns land IN FEE totalling 331 Acres and renting or leasing out land and houses, in the Townland of Cloonamahon in the Parish of Ballysadare. Henry Meredith is one of his renters.
Also in Cloonacurra Townland is John Ferguson.www.askaboutireland.ie
for further details.
Tithe Applotments 1820-1839 www.genealogy.nationalarchives.ie
1901/1911 Census: www.census.nationalarchives.ie
It doesn't appear there are any Meredith's in Sligo's telephone book. 2 Ferguson's.
If Meredith had an 'estate' you could look inwww.landedestates.ie www.irelandxo.ie www.censusfinder.com
I have an old CD set that the Latter Day Saints used to sell but now unavailable. The dates are 1864-1875 only. If you have anyone who fits in those dates I can look them up.
Also Church of Ireland marriages 1845-1862 are on the CDwww.familysearch.org