Zippi,
I am by far no expert with gas engines, but from what I've read, it looks like you have plenty of open cowl for air to exit, but almost nothing for air to get in at the cylinder. Only open at the bottom creates a low pressure area and the air around the cylinder just stagnates causing the hot running. It's the same thing I run into with my old British sports cars that have a reputation for overheating.
Mike MacLean