Having cruised the Trent-Severn Waterway, the Rideau Canal, the Georgian Bay and the west side of Lake Huron from Port Huron to the Straits, I believe there would be no significant difference in slip availability based on a 36 ft versus a 42 ft boat.
The canals present many wonderful opportunities for tying up along lock walls surrounded by beautiful and peaceful parks, and for tying up on city walls in the heart of cities and small towns. None of these walls have length restrictions.
The Georgian Bay (northern end of Lake Huron) has some of the most beautiful anchorages you will encounter anywhere. Scattered within the 30,000 islands, there are marinas just as modern and complete as those found elsewhere.
Michigan has been aggressively rebuilding all of their marinas and have moved to substantially improved sea walls and floating docks.
What is causing your concern?