Here's what you do. Bid as high as you want, or as low as you want.

CM load factors are hovering around 75% IIRC from an article I read recently. There's also a lot of...maybe random flights CM has, like MSY-PTY, BOS-PTY, YUL-PTY. I'm not saying the flights aren't good or profitable, but is there that many people daily going BOS-PTY-_____ there's certainly easier ways to get to SA.

I've only bid twice and both times I bid as low as possible and got them both. Now those were PTY-MDE flights, so they're short and frequent but Copa also feeds you in economy and has free booze. I like their service in J/Y and the aircrafts either have AVOD or don't, no difference in business. So the biggest difference in business is a better meal and a bigger chair (that doesn't lie flat).

Point is, J is nice, but really not necessary. Bid as low as possible and hope you get it!

The biggest upside to the upgrade, is that you get the bonus miles (at least I did, glitch perhaps?), I checked my aeroplan account after and got credited as C class as opposed to the K or whatever I originally booked. But again, even if you're stuck in Y, there's really good odds you'll get a middle seat empty and you can pick an exit row seat for free as well in my experience.

Edit: I do recall bidding the lowest once and not getting it, but CM doesn't usually fly with empty J seats so if you bid and there's an open seat and no one else bids, they'll take yours.