Steve, this is splitting some pretty serious hairs, and I'm not really sure where I stand on this, but, while we're on the topic of proofing trays, it looks like your dough balls, by the time they fully proof, will contact the walls.
I know that most forum members, myself included, have containers where the dough typically touches the walls, but, I have seen some NP pros (such as Roberto) talk about using the top of the dough ball (as it sits in the tray) as the top of the pizza, since the bottom of the ball is pockmarked and less aesthetically pleasing. When the dough creeps up the walls of the container, you're basically maximizing this pockmarked area.
I know Craig makes flawless pies with dough touching the walls of the container, and we also have members that don't follow the Roberto approach and make beautiful pizzas as well, but it is something that I think about.
Another advantage to having non touching dough balls in trays, is that, for most doughs, you can get the dough up with a scraper without having to pre-oil the tray. When you get into individual containers, that typically requires oiling to get the dough out.