a place for zinesters - writers and readers
It kind of depends on what's more important for the carry-on: clothes or stock. But just looking at your catalog right now, even if you're only carrying 5 copies of each zine, they probably aren't going to fit into a 21/22-inch roller suitcase. You probably would need the 26-inch roller suitcase.
Or a steamer trunk, but those have to be a pain in the ass to carry around.
You might want to invest in the big roller suitcase now anyway. Once you reach a certain point in your distro (like over 200 titles or items), having a rubbermaid container box isn't going to cut it anymore. They pop open a lot if they're full, and it doesn't matter if you sit on it while trying to keep the handles down. I had that problem with my distro stock and taking it to the first Philly Zine Fest.