As you discovered, you can't infer the temperature in the carburetor based on the temperature on top of the glowplug. Most Novarossi engines have all-metal carburetors which absorb more heat from the crankcase and will cause the fuel to boil more easily. I always prefer composite carburetors when the option exists, but if there is no composite carburetor for one of my engines, I can just tune the carburetor ever-so-slightly richer to make sure the carburetor never gets hot enough to boil the fuel.