Why not just throw some panamax locks in at Montreal/Quebec City, and then run them up the Ottawa. That way Renfrew and Mattawa can get shipments in on time
We could go all the way through the French River system like was planned, to avoid those pesky Americans.
We can also upgrade the Rideau Canal system to Panamax while we're at it. You know, it would only be like, one lock downtown, and maybe one additional lock somewhere along the line. Just need to blast out a bigger turning bay in front of the Chateau, not sure if the Ottawa river is wide enough for a ship to turn there!
Fun to think about what it would look like, though!