Captain Cook graving dock in Sydney had a length of 347m and width if 41m in 1980. I don't know about Canada, but 960ft was and apparently still is the maximum length a warship can be to fit into British docks.
Yup, it's going to be a squeeze but i'm sure it can be done. This is Britain we are primarily talking about here and ways around the porblem can be found. Our Military is told to work on the principle of "do the Job with what you have, no what you need".
Another thing is that the CVA-01, despite weighing in a more than 63,000 Tons at full load actually had a more or less identicle draught to HMS Eagle and Ark Royal on account of it's larger hull-to-weight ratio. Eagles final draught was 11 meters while CVA-01 was 10.2 meters. It is more as you put it an issue of size that has to be overcome.
Russell