It is true that there are fewer seats to go around at that time, but schools typically end up accepting about twice as many students as actually decide to attend, since many will have multiple acceptances. Since the cycle is also long at other DO schools (that is, the same pressures are at work there, too) your assumption doesn't work out in practice. I can name a few people with perfectly average DO stats who weren't accepted until later on in the cycle.
Not to say that I would wait around just for fun!
I wouldn't do it. I figured that they meet a TON of people, a new set every week. It won't help you, and it just adds to their pile of mail to open. If you have a particular reason to thank a particular person, that is different. But if it is just for doing their job... well, I hope you gave them a hearty and sincere thank you when you shook their hands after the interview. That would have counted for more than any card you could send now.
Look... an average is just that. Half of the students admitted will have below average scores, so that alone isn't going to hurt you. Be less worried, relax, and interview well.
Getting an interview here DOESN'T mean you are in. It means that you have a real chance, and if you can just be a friendly person who communicates pleasantly with others, you will probably get the seat. Some schools don't screen... they do invite just about everyone for an interview. Ask Goro about how he feel about that.
LECOM does pre-screen. If you get an invite, it means they like you and want to meet you. I think a good interview here is really meaningful... and a good interview is one where you are relaxed and professional throughout.