HIS Mephisto came with an aluminum carb. He already said that earlier in the thread.
I'd be wondering what made the metal carb get hot enough to boil fuel.
Probably the body shell was redirecting air around the base of the engine so the carburetor wasn't getting blasted with direct high-speed airflow. Some people might choose to blame it on the user, but people who actually design engines clearly think otherwise. It's not like he's the first person to have problems with an aluminum carburetor overheating. There's a reason why even high-end engine manufacturers are switching to composite carburetors, and why O.S. started equipping the mounting collars of their aluminum carburetors with composite insulators a long time ago.