It has been several decades since my studies of isostatic rebound, but as I remember, what is happening is that the rebound further south is pretty much done in comparison to further north. The result is the land is slowly tilting with areas to the north getting higher which tends to drain Huron more. Not saying that dredging has not had an impact, but if it did have a huge impact then Erie would be much fuller than it is.
Back in the water in Grenada - with new main and #2 and cockpit canvas (Santa came early). Will spend the winter and early spring in the Caribbean and then head to Bermuda and the northeast US. Still trying to decide if we will bring the boat to Canada, either in 2015 or 2016.