Hi Hugh, Sorry for long delay but I've moved house.
Borrisoleigh is not far from my ancestral village - ten miles . I wish I had instant answers or you.One thing I recommend now is to check out the site down the page under Nancy Custers contributions - i.e. ask her about DNA to see if you connect with any other D'arcy/D'Arcy/Darcy family from Ireland. I'll re-read your notes on your ancestor.
Only other suggestions are to check from the known backwards shipping/tax/births/marriages/schools/cemetery/death records etc and any old relatives or friends of the person.
Hope you succeed. I find it like a large jig saw puzzle and its great to "find" two new pieces. Bernie