The carb fridge is meant to isolate the rear carb from the engine hot air. Purpose is to prevent vapour lock, and keep the carb functioning well. In the last two pictures I show how to block off the last tiny bit of hot air. MVVS does not use a carb isolator block. It is not needed as long as the carb resides in cool air. However, the combination of warm air and engine heat may cause problems, so I rather be safe than sorry.
PS
Material used for the fridge is 5-ply balsa, which I stumbled across in a hardware store. It holds screws very well, and is stable in all directions.

Every part can be disassembled in order to access engine and throttle setup. The last air blocking parts are best glued to the engine rear mount. First tests will be without blocking the last bit of hot air to the carb. If all is well, no further actions will be needed.