Pat, as you will have seen from my reply to Donna, my e-mail is playing up, but I am hoping to be able to reply to you that way soon.
Your point is of general interest. At one time the IGI was a straightforward transcription of records, mainly baptisms and marriages from the parish registers. Any mistakes were usually caused by transcribers ignorant of the Isle of Man misreading difficult handwriting. Now the IGI has been contaminated by what researchers have added, sometimes without any foundation. Other readers may correct me, but I reckon that dates of birth in the IoM in the 16th century or earlier are worthless.