It's certainly not too late to write to POI's. I'm sure some people will disagree with this, but every professor I've spoken to has said not to include attachments in your initial e-mail. I've read here on the forums of people who attached their CV and had success, but my profs seemed to consider it more of an annoyance. I've been sending an e-mail with just 2-3 sentences summarizing my research interests and experience, then a couple of straight forward questions like if they're accepting students or other faculty they think may align with my interests, and I've had a great success rate - 7 responses out of 8 contacted. 1 was the generic "looking forward to your application" response, 2 gave info that helped me scratch programs off my list, and 4 have turned into longer exchanges.