512 shouldn't be an issue. A few people here have already reported 512s that work well. I tried to find the GDoc with the verified working models, but I don't have time to dig deep enough for it. If you search the wiki, you should find a page about working accessories with the link.
I don't believe there's been any indication of a maximum size, yet.
I don't believe there's been any indication of a maximum size, yet.