I have run the Cool Carb plate on my 340 for about five years or so. It does cool the carb! I have stopped the car in a parking lot, opened the hood to feel the carb to find it cool and sweating. It was strange. But it does get hot after a normal cool down process. But while driving, it seems to make a difference with the air passing around it.

There is a max temp that CC specifies. Get your tuning correct and you should not have problems. I have had manifolds, iron J heads, aluminum heads, and headers on this engine and each time I pull the carb I make an effort to check the spacer plate. I have not had any problems but others will show pictures of the spacer plates melting.
The owner is a nice guy and I would suggest to ask him what his max temp is and decide from his answer. He has a cool story on how he chose this material. 👍. If I remember correctly, it was used as a heat sinc material where he used to work.