Hi.
I have an interest in Derrylossary as my GGGG grandparents Henry and Elizabeth Webster are buried there and I am lucky enough that there is a headstone that can still be read. It is only about two weeks back that I visited the RCB and had a look at all that they have on Derrylossary. I had previously examined the Registers of which the earlier years no longer exist but there were snippets to be got from the Preachers Books and the Vestry Books are in quite good condition and not too hard to read. To be found in the Vestry Books for the early 1800's are lists of parishoners and the townlands where they lived , probably info mixed with the tithes. There is a folder containing documents , some dating pre 1800 , but they are only a few with most of what is to be found here quite modern. If you are looking for families here that are not to be found in the Registers that exist, it is worth looking at all the other material , although it will take time.
John