Coming to this late but...
You have Achill names in your profile and the Masterson book is a lor easier than other avenues for this place: records colllated in family groups with baptism and registration dates, and often godparents. If you know the place it also makes it easier to interpret the importance of baptism before registration date, and ruling out namesakes who died in infancy.
On Ancestry there are people who can scan and send you info. No payment.
The records are good for Achill