I believe the Canadian uses the Manor Sleepers on the Canadian, during the Off Peak Season. With the Cabin for One accommodation, are the four rooms all more or less, over the wheel set ? I'm thinking specifically of Room # 3's location.
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They say the most comfortable bed on the train is the lower berth, and I agree. If you can do without an electric plug and a private toilet, it's the way to go. Try for the one near the shower, farthest from the trucks.
The diagram does not show accommodation numbers, but a call to VIA will help you.