Your best bet is to call for the upgrade the instant you can, i.e. 72 hours. Back in the old days, I used to call at about 72 hours and 2 minutes, and then the agent would just keep me on the line. That way, I could make sure I was first in line. I know that on occaision, all the upgrade seats have disappeared within a few minutes of the cutoff time.

Upgrades are fairly easy to get for golds. The only times you might have problems is on busy 737 flights (YYZ-YHZ, YVR-ORD, etc) and sometimes at Christmas. For YYZ-YVR, upgrades are almost a certainty, especially if you call early.

The best plane for YYZ-YVR, in my opinion, is the DC10, usually 1 or 2 flights a day using this plane. It has far more b/c seats than, heaven forbid, a 737. But the real benefit is that you get the Club Empress service -- HUGE seats, tons of room, and in seat video, just to mention a few benefits.

Second choice would be a 767, particularly an A seat (i.e. 3A) as they are single seats, with a big "glove box." The only difference is they do not have in seat videos. They do have Sony Watchmans, that they sometimes make available.

Third choice would be an A320, especially once the new seats are installed. They have about the same number of b/c seats as the DC10 and 767.

Finally, anything else, which pretty much means 737. There are no direct flights using this plane anymore, but you might find yourself on one if are on a connecting flight.

Right now, aim for the DC10.

But all this changes big time on April 5. That day, they will begin 747 service on that route. (4 days per week) This plane has almost double the b/c seats that either the DC10 or 767 have, and they DO have the in seat video.

Finally, if you want to get an idea of how many upgrade seats are available, you can use www.itn.net or www.travelocity.com to check seat maps. You need to "pretend" to hold or purchase a ticket. Just cancel the transaction once you have seen the seat map.
Bear in mind however, that sometimes seats are sold without being assigned, although on CP in business class, this is not too common. I *think* the limits are 2 seats on 737s and 3 seats on bigger planes are held as revenume seats until two hours before flight time.

Another option is too book the flight you *want* to take, and then be prepared to do a same day standby on a different flight, if there are upgrade seats available on that flight. This works especially well if you book a late in the day flight, and show up at the airport earlier. You may end up "hanging around" the airport for a few hours, but with Gold, you'll at least have access to Canadian's superb lounges. (Vancouver's lounge is worth going to very early to just enjoy it. The other's won't be far behind.)