SD slot capacity

Hello, folks. I've been corresponding elsewhere about the SD slot specs for my C7, with no definitive answer about just how big a card it can use. HOWEVER, one person told me that he was successfully using a 64GB card in his unit!
What I'd like to know is if anyone here has also done this or better...are there any photographers out there who have tried maybe a 128GB or 256GB card in there?
Not that I can afford an SD card that costs more than the Chromebook itself, lol, but I would like to put in the biggest I can afford and just leave it in the slot as a secondary hard drive. "Official" specs though (as far as I've been told) only state a 32GB capacity. If this other guy used a 64GB, then there's the distinct possibility that even bigger cards will work.
And, of course, it would just be nice to KNOW THE FACTS about what will and won't work.