Hi
I have the carb spacer in a Weedeater 25 and it helps isolate carb from heat of cilinder.
If the heat transfered to the carbureter is enough you can make the gas start boiling and you dont have reliable run.
The gas boiling is a problem in old cars with carbureters. The Fiat car , here named 125 mirafiori with DOHC have carb with recirculating gas system to avoid gas boiling.
Happy flying
Jose