Its funny, I cant really imagine it as a cairn kerb, the stones are all so much like pillars. They seem to have been picked for their jagged appearance and interesting shapes, the greatest visual impact would seem to be against the sky rather than studded around a mound. Thats a more intuitive idea though!
I must stop at Annaghmore Glebe next time I'm up that way, is it anywhere near Reyfad?