Registry of Deeds, Ireland

When both Claire Santry and John Grenham write about an Irish resource you know something interesting is happening.
Claire writes about the 21 February update to the Registry of Deeds index project with 225,142 index entries from 25,551 memorials of deeds.
John Grenham celebrates the availability of microfilm image files through FamilySearch.
Claire points to a helpful guide to using the virtual microfilms of Registry of Deeds books.
I've not had a chance to test these on my elusive John Marmon, or more likely his father Peter (maybe), in County Down. It's likely my last hope.