Kevin, have you ever considered a trip to Longpoint, Ontario, or as others have stated, hunt the same birds on the U.S. side?
Paul, rather than get into a discussion on whether a scaup is a greater or lesser, based on head shape with a C.O. down the road, you would be better served to go by the extension of white coloration along the primary feather shafts on the wings.
Longpoint was my go to spot for over twenty years. I have rarely (if ever) harvested a canvasback there although I know some are taken. Redheads can be plentiful in late October or early November if you hit it right and scaup are common. It has the same rules as the Ontario side of Lake St. Clair but is much larger. It can be just as difficult to find a good spot and I would much rather deal with the "locals" at LSC. My experience with late season hunting is much better on Lake St. Clair.
Longpoint Redhead
Longpoint Watch at the Head of the Bay (had to throw that one in, it is one of my favorites)
LSC hunt Nov 2011