I'd like to add a roller bag to my travel arsenal, but I'd prefer it to be small: 18-19" tall if possible, or even shorter, and more importantly, thin. I've noticed that most rollers are about 8-9" deep, and I'd like one that's 7". 7.5", for instance, was the depth recommended by IATA in their short-lived cabin-friendly initiative, and it seems like a good idea. That size would be more versatile and more likely to squeeze into a packed overhead. I have searched online and visited Marshall's, and haven't found anything like that. If you know of one I'd appreciate it!
I already have a 19" Osprey Ozone, but my problem with it is that it doesn't have a rectangular design that lets you easily stack a personal bag on top. It's also kind of delicate and I'm always afraid it won't survive gate-checking, so I only take it on those rare flights when I need a roller and I am sure there will be space on top.
I've been carrying everything in Tom Bihn soft-sided bags, which I love, but I'm getting to the point where back problems are convincing me that I need a decent roller to rely on as well. Two wheels or four -- that doesn't matter to me.