As far as a depth chart for Magog .... I did a google search and found one made over 50 years ago from a Canadian guy. You'll know the one when you see it .. .it has straight lines from center points ... usually island and other points of reverence. It's not done with with cont. lines like a topo. map like most others you see. The problem Big G is I don't think it has South Bay on it. It is on two pages on the web and stops at the city of Newport. Let me know if you cant find it from Google and I will try and send you the address.
KP