He might be able to drop a 4 credit class and add a 1 or 2 credit class to stay full time. Some schools have them. My college offered these 1 credit geology classes that just lasted half the semester — one semester I took a couple of them, One was the first half of the semester and one was the 2nd half. You want to make sure an added class counts in the total for FA (like a sports/gym class might not).