Hi MaCo546, I'm a Gagnon too! I wonder if you have reached out to the "Gagnon Family Association" located in the province of Quebec? They could help you perhaps, at least to post your question to their membership? They also have a genealogist. Here's the website and Facebook page:
https://www.facebook.com/groups/lesfamillesgagnonetbelzilein...
http://gagnon-belzile.com/
They have english speaking people who i'm sure can help!