Thank you Susan for your response and the additional information.I have seen Gary Calder's wonderful paper and agree that it is an excellant piece of work; I feel that it is the most informative & compelling presentation I have yet to encounter.
It does of course support the likelihood that William was born about 1631/32... based upon the abduction of John Colquhoun's sister-in-law, for which formal charges were brought against him.
But of course, as you pointed out, and he does as well, the bottom line remains that there is no known discovery of record for the birth of our William.
Please keep me on your mailing list, as I would love to receive any additional information that you might come across and care to share. :)