Cocothrinax argentata is remarkably hardy. We have one that's been subjected to many nights in the high 20's with no complaints. However, down around 25, they get scorched pretty bad, especially with frost. In contrast, C. barbadensis is a cold weather wimp. It starts spotting below 40. Old leaves begin dying after a temp near freezing. I don't think it'll take a subfreezing event well at all. I suspect at 28 its totally defoliated, and at 25, it's probalby just a bean pole. I suspect by Jan 15, you'll be able to tell if its a "barbie".